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                Speciation in the Brazilian Spiny Rats
                (Genus Proechimys, Family Echimyidae)

                                  BY
                             JOÃO MOOJEN


                  University of Kansas Publications
                      Museum of Natural History

        Volume 1, No. 19, pp. 301-406, 140 figures in text
                          December 10, 1948


                        University of Kansas
                              LAWRENCE
                                1948




    UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

        Editors: E. Raymond Hall, Chairman, A. Byron Leonard,
                          Edward H. Taylor

     Volume 1, No. 19, pp. 301-406, 1 plate, 140 figures in text

                    Published December 10, 1948


                        UNIVERSITY OF KANSAS
                          Lawrence, Kansas


                             PRINTED BY
                  FERD VOILAND, JR., STATE PRINTER
                           TOPEKA, KANSAS
                                1948

                               22-3343




               Speciation in the Brazilian Spiny Rats
               (Genus Proechimys, Family Echimyidae)

                                  By
                             JOÃO MOOJEN




CONTENTS


                                                           PAGE
  INTRODUCTION                                              305

  METHODS AND TERMINOLOGY                                   305

  ACKNOWLEDGMENTS                                           308

  PALEONTOLOGY                                              308

  SPECIATION                                                311
      Subgeneric variation                                  312
      Specific variation in the subgenus _Proechimys_       314
      Subspecific variation in the subgenus _Proechimys_    317
      Specific variation in the subgenus _Trinomys_         320
      Subspecific variation in the subgenus _Trinomys_      322

  TAXONOMIC CHARACTERS                                      323
      Size and proportions of external parts                323
      Pelage                                                324
      Skull                                                 326
      Incisive foramen                                      326
      Teeth                                                 327

  HABITS                                                    330

  CHANGES WITH AGE                                          331

  Genus PROECHIMYS                                          333

  ARTIFICIAL KEY TO SUBGENERA AND SPECIES                   334

  Subgenus PROECHIMYS                                       338
      _Proechimys goeldii_                                  338
          _Proechimys goeldii steerei_                      338
          _Proechimys goeldii goeldii_                      340
      _Proechimys semispinosus_                             342
          _Proechimys semispinosus liminalis_               343
          _Proechimys semispinosus amphichoricus_           344
          _Proechimys semispinosus kermiti_                 345
      _Proechimys longicaudatus_                            346
          _Proechimys longicaudatus brevicauda_             349
          _Proechimys longicaudatus boimensis_              350
          _Proechimys longicaudatus longicaudatus_          351
          _Proechimys longicaudatus leucomystax_            352
          _Proechimys longicaudatus roberti_                353
      _Proechimys guyannensis_                              355
          _Proechimys guyannensis villicauda_               355
          _Proechimys guyannensis ribeiroi_                 361
          _Proechimys guyannensis hyleae_                   361
          _Proechimys guyannensis nesiotes_                 363
          _Proechimys guyannensis leioprimna_               364
          _Proechimys guyannensis oris_                     365
          _Proechimys guyannensis arescens_                 366
          _Proechimys guyannensis riparum_                  367
          _Proechimys guyannensis arabupu_                  369

  Subgenus TRINOMYS                                         369
      _Proechimys dimidiatus_                               371
      _Proechimys iheringi_                                 373
          _Proechimys iheringi iheringi_                    378
          _Proechimys iheringi bonafidei_                   378
          _Proechimys iheringi gratiosus_                   379
          _Proechimys iheringi panema_                      380
          _Proechimys iheringi denigratus_                  381
          _Proechimys iheringi paratus_                     382
      _Proechimys setosus_                                  384
          _Proechimys setosus setosus_                      385
          _Proechimys setosus elegans_                      387
      _Proechimys albispinus_                               388
          _Proechimys albispinus albispinus_                390
          _Proechimys albispinus sertonius_                 391

  INCERTA SEDIS                                             392
      _Proechimys myosuros_                                 392

  CONCLUSIONS                                               393

  TABLE OF MEASUREMENTS                                     395

  LITERATURE CITED                                          400


[Illustration: FIG. 1. _Proechimys dimidiatus_ (Günther). Live female on
left and male on right. ×1/2. From Tingua, Nova Iguassú, Rio de Janeiro,
Brazil. Photographed in spring (August or September) of 1942 by
author.]




INTRODUCTION


The spiny-rats included in the genus _Proechimys_ are common in almost
every forest of South America above the Tropic of Capricorn, and in
Central America northward to approximately 12° N, in Nicaragua. In size
and proportions they are similar to the brown rat _Rattus norvegicus_
but actually they belong to a very different suborder of rodents--the
Hystricomorpha. The hystricomorphs are represented in South America by a
large variety of animals, of which capybaras, agoutis and cavies are
common representatives.

The pelage of the spiny-rats has a large number of flattened, spinelike
hairs, especially on the back. The color ranges through different tints
and shades of reddish-brown more or less evenly distributed on the upper
parts; the underparts are usually pure white, sharply contrasting with
the brown color above. The tail is bicolored, brown above and white
below.

The spiny-rats live in forests of different types, generally in the
proximity of water. Shelter is usually procured under boulders, stumps
or masses of roots. The reproductive rate is low; on the average, there
are only two young per litter and only two litters per year.

Sixty-odd names have been given to species and subspecies of
_Proechimys_ in the last hundred and fifty years and no serious revision
of the taxonomy of the genus was undertaken in the last century. The
purpose of the present work is to provide means of understanding species
and subspecies within the genus and to describe the different kinds
known to occur within the confines of Brazil.




METHODS AND TERMINOLOGY


      PELAGE.--It was found advisable to use a standardized nomenclature
      for hairs. The names here proposed are a choice of those used in
      the literature, with the suffix "_form_" as an element of
      uniformity. I feel that it would be advantageous if everyone
      adopted a similar universal system in mammalogy.

      The names listed below are used as nouns and are considered as
      English versions which could easily be adapted to different
      languages. These names may be complemented with adjectives as
      needed. Examples are lanceolate aristiforms, spinous aristiforms,
      and woolly setiforms.

      _Aristiforms:_ The most conspicuously developed hairs in a
      three-layered pelage or the corresponding hairs in a simpler
      pelage. Names previously used for these hairs are: guard hair,
      leithaar and jarre.

      _Setiforms:_ Common to all species and most numerous throughout the
      pelage; second in conspicuousness, being the dominant hairs in the
      middle layer. Synonyms are: over hairs, grannenhaare and soies.

      _Villiforms:_ The smallest hairs in the three-layered pelage.
      Synonyms are: underfur, wollhaar and duvet.

      _Vibrissiforms:_ The vibrissae proper, or any typically sensory
      hair.

      TEETH.--The tritubercular nomenclature was abandoned because of
      overwhelming difficulties; more research on the Hystricomorpha is
      certainly needed before the tritubercular nomenclature can be
      applied with confidence. The following names are used for features
      of the molariform teeth:

      _Main fold:_ The inner or lingual fold in the upper molariform
      teeth and outer or labial fold in the lower molariform teeth.

      _Counterfold:_ Any outer or labial fold in the upper or any inner
      or lingual fold in the lower molariform teeth.

      For incisors Thomas (1921:141) is followed: _opisthodont_,
      _orthodont_ and _proodont_ depending on the angle between the
      exposed part of incisors and the ventral surface of the rostrum.

      The capital letters P and M designate premolars and molars,
      respectively, of the upper jaws; lower case letters p and m
      designate corresponding teeth in the lower jaws.

      MEASUREMENTS.--Measurements of skins were used only when provided
      by the collector. The length of the hind-foot is intended to be
      always _cum unguis_, but in a few instances it is impossible to be
      sure whether the collector included the nail. Length of tail was
      used only when the tail seemed not to be mutilated. Ear
      measurements taken by collectors are scarce. In spite of the
      apparent usefulness of length of ear, it was found to be
      inadvisable to take the measurement on the dry skins.

      The following measurements of the skull are used in the tables:

      _Greatest length:_ From the anteriormost part of the nasals to the
      posteriormost part of the supraoccipital.

      _Condylo-incisive length:_ From the anterior face of one incisor,
      at the alveolus, to the posteriormost part of the exoccipital
      condyle of the same side.

      _Zygomatic breadth:_ Maximum distance across zygomata in a plane
      perpendicular to longitudinal axis of the skull.

      _Length of nasals:_ Maximum length of one or both, whichever is
      the greater.

      _Interorbital constriction:_ Least width between the orbits on top
      of the skull.

      _Palatilar length:_ From the posterior face of an incisor, at the
      alveolus, to the nearest part of the posterior edge of the
      palatine bone.

      _Crown length of cheekteeth:_ From the anterior border of P4 to
      the posterior border of M3.

      In the accounts of species, measurements of aristiforms and
      setiforms are used. The hairs measured were taken from the
      middorsal region and outer thighs, and the measurements are means.

      All specimens of which measurements are here recorded, as for
      example in the tables, are fully adult; each specimen shows some
      wear on each of the four upper molariform teeth unless otherwise
      indicated.

      Capitalized color terms are after Ridgway "Color Standards and
      Color Nomenclature," Washington, D. C., U. S. A., 1912. One
      setiform was taken from the animal and placed over the rectangles
      in Ridgway's charts and the examination made under a microscope
      with low (×7) magnification and natural light. This method was
      found to give the most satisfactory results.

The following abbreviations are used for names of institutions:

     AMNH--American Museum of Natural History.
     CNHM--Chicago Natural History Museum.
     DZ--Departamento de Zoologia da Secretaria de Agricultura, São
         Paulo, Brazil.
     MCZ--Museum of Comparative Zoology at Harvard College.
     MN--Museu Nacional, Brazil.
     MZ--Museum of Zoology, University of Michigan.
     SEPFA--Serviço de Estudos e Pesquisas sobre a Febre Amarela, Brazil.
     USNM--United States National Museum.
     UZM--Universitets Zoologiske Museum, Copenhagen.




ACKNOWLEDGMENTS


      Approximately two thousand skins and skulls were assembled at the
      Museum of Natural History, University of Kansas, through the
      coöperation of the authorities in the various institutions of North
      America, Brazil and Denmark, as listed immediately above. This
      comprehensive material was used to obtain a more complete
      understanding of the group, and for the loan of these specimens I
      am extremely grateful to the authorities of each of the
      institutions.

      First of all I acknowledge the encouragement given me in the
      _Proechimys_ project by Heloisa Alberto Torres, Director of the
      Museu Nacional, Rio de Janeiro. I extend my thanks also to Stephen
      D. Durrant, of the University of Utah, for helpful corrections in
      the preparation of the manuscript; to Mrs. Virginia Cassell Unruh,
      for the preparation of the drawings of the skulls; to Miss Alice
      M. Bruce for assistance in drawing the maps; and to my daughter,
      Julieta, for help in assembling data and for typing.

      Dr. Remington Kellogg, Curator of Mammals in the United States
      National Museum, and the late Dr. Wilfred H. Osgood, formerly
      Curator Emeritus of the Department of Zoology in the Chicago
      Natural History Museum, generously permitted me to use their
      private lists of South American mammals. These lists contain much
      unpublished data, as for example, proof, in Kellogg's list, that
      _Proechimys guyannensis_ (E. Geoffroy Saint-Hilaire, 1803)
      antedates _P. cayennensis_ (Desmarest, 1817). I register here my
      gratitude to both these zoölogists and acknowledge other critical
      assistance from Dr. Kellogg.

      The John Simon Guggenheim Memorial Foundation awarded me a
      fellowship for which I am deeply grateful. This expression of the
      Foundation's interest in education and good neighborliness made
      possible the completion of the present paper.

      Finally I desire to express my deepest gratitude to Professor E.
      Raymond Hall, Director of the Museum of Natural History and
      Chairman of the Department of Zoology at the University of Kansas
      whose untiring aid and guidance has enabled me to terminate this
      study.




PALEONTOLOGY


The only known, significant, fossil _Proechimys_ comes from deposits in
the limestone caves of Lagoa Santa, Minas Gerais, Brazil. These
deposits, of Late Pleistocene or Recent age, were extensively studied by
P. W. Lund and the results published in a series of French and Danish
papers. F. Ameghino (1934:110) studied another fauna from a deposit of
similar age in the cave of Iporanga, São Paulo, Brazil. _Proechimys_ is
recorded in his account under the inclusive specific name _fuliginosus_.

The molariform teeth of the fossil described by Lund (1841:pl. 21, fig.
14) shows its close relationship to the living form _P. s._ _elegans_
(Lund) which still inhabits the same region. It belongs in the more
specialized subgenus _Trinomys_ which seems to have been derived from
_Proechimys_. _Trinomys_ has the main fold in the molars always greatly
developed and the fold tends to set apart one lamina in the occlusal
surface. The Lagoa Santa fossil, like some specimens of the living
subspecies, has a small main fold in P4. However, the main fold is large
in all upper molars and in the lower molariform teeth which are notably
specialized in the extreme reduction of the number of counterfolds to
only one.

One hypothesis concerning the evolution of the genus is that a more
primitive group of _Proechimys_ lived in all of the Central Plateau of
Brazil in the Pleistocene Time. The climatic conditions at that time
might have been such as to support large forests but, since the
Pleistocene, these climatic conditions may have changed from humid to
the present drier conditions, which support the dominant, savanna,
floral climax. Actually the extinct fauna from the caves includes
animals which have disappeared from the area and now live only in more
humid areas, as for example _Myocastor_, which has shifted to the
lowlands to the west and south.

Possibly climatic changes were responsible for the faunal shift from the
region that is now a plateau in Central Brazil. This climatic change may
have resulted from the gradual uplift of the eastern part of the
continent. This uplift prevents part of the trade winds which come from
the east from carrying the same amount of moisture inland as they did
previously. In fact, the Andean revolution, even if it occurred as late
as Late Tertiary, would have had no perceptible influence on the
amount of water precipitated on the more eastern parts of the continent.
Oliveira and Leonardos (1943:617) point out that after a Cretaceous
submersion of the central part of Brazil, there was a general uplift.
The authors (_op. cit._:689) mention the presence of continental
Cretaceous deposits in the Central Plateau of Brazil, in support of
these changes, and state that "pelo menos em certas zonas do litoral a
elevação do continente prolongou-se até o Pleistoceno."

Berry (1942:373) concluded, among other things, that there was a
southward extension "in South America of equatorial floras in the lower
Miocene," and (_op. cit._:372) that ... "east of the Andean Axis in
the south temperate zone there was a normal mesophytic flora ... instead
... of present day large steppes."

My idea is that a tropical forest still covered the Central Plateau of
Brazil in (early?) Pleistocene times and that populations of
_Proechimys_ of a primitive type, similar to _P. g. steerei_, for
example, lived in that extensive forest-climax. The gradual uplift of
the plateau, however, gradually brought about drier conditions in this
region. As a result a large cliseral change was initiated, which shifted
the forest-climax to the more humid eastern escarpments and lowlands
that were gradually being developed, while the savanna climax was being
established on the plateau. Eventually the effect of the decreasing
moisture was locally accentuated by the erosion of the sandstones
(Oliveira and Leonardos, 1943:690) in northeastern Brazil, thus
depriving it of a natural reservoir of rain water. An arid belt was
developed which now constitutes an efficient geographic barrier to the
distribution of many kinds of animals.

One marginal species may have shifted eastward with the forest-climax
to effect the Recent distribution. The eastern species became completely
isolated from the main group, accumulated mutations, and evolved into
the subgeneric type _Trinomys_. The generic trend that gave rise to
_Trinomys_ probably remained more stable as far as supraspecific changes
are concerned. The lack of barriers in the distributional area of the
original group favored the dispersal and submergence of mutations and,
therefore, there was but little further supraspecific evolution. The
speciation in both subgenera finally resulted from gradual
differentiation of varying populations since they show combinations of
the generic biotypes and possess few truly qualitative characters.

The cliseral changes in the Central Plateau, which developed the dry
belt, a barrier, might explain the evolution of a few more supraspecific
groups of mammals, as indicated by the presence of similar forms in the
Amazonian region and in Southeastern Brazil. Among these _Echimys_ and
_Phyllomys_, in the same family with _Proechimys_, show differences that
are parallel to those observed in _Proechimys_. One of these parallel
changes is the increased lamination of the cheekteeth. Although
_Echimys_, from the Amazonian region, has upper molariform teeth with
the four laminae fused, _Phyllomys_ has the four laminae completely
separated.

None of the genera known from the Upper Oligocene and Miocene of
Argentine deposits seems to be directly ancestral to _Proechimys_.




SPECIATION


The detection of differences of systematic worth between populations of
animals, represented by skins and skulls, is a step preliminary to
deducing the factors responsible for the differences. Ordinarily the
factors which cause heritable differences have to do with geographic
isolation and adaptation to ecological conditions. When differences in
the structure of the animal are known, a person is led to speculate on
the factors which could cause them. For one thing, does the observed
degree of difference tend to isolate animals possessing the "new"
character from the other animals? It would seem to me that the isolation
once started by one of these differences tends to be accentuated with
time and the difference itself thus then becomes a factor responsible
for further differentiation.

Whether or not transition from one character to another occurs
gradually, in its geographic expression, and thus whether or not
intergradation occurs between two subspecies, can be ascertained by the
analysis of a series of population-samples appropriately distributed
geographically. If two characters of systematic worth are known to blend
in one part of the geographic range of a subgenus, and if the same two
characters are seen in two other populations, far removed geographically
from each other and without any samples of annectent populations to
provide actual evidence of intergradation, then such intergradation is
to be inferred.

The available collections of _Proechimys_ mostly were made haphazardly
with the result that there are extensive areas from which no specimens
as yet are available. Thus, actual proof of intergradation is often
lacking in areas where it almost certainly occurs. In some extensive
areas, however, many samples, from relatively regular intervals, have
been available and they provide genuine proof of intergradation. These
instances have served as a guide for estimating whether other samples
should be considered to be full species or instead merely subspecies of
the same species.

Lack of intergradation in any of the characters may be accepted as the
criterion of full species. Where two populations occupying the same
range (sympatric populations) show different qualitative characters,
they almost certainly do not crossbreed. Furthermore the characters that
distinguish such kinds of nonintergrading animals are likely to be
considered as of full specific value when detected in far distant parts
of the range of the subgenus.

In a genus that is widespread and continuously distributed, it is useful
to know which characters always distinguish full species and which ones,
sometimes or always, distinguish only subspecies, since in a population
from a small island, there is, ordinarily, less individual variation
than in a corresponding population from the mainland or a larger island;
under certain circumstances a person might be tempted to give specific
rank to the population when its characters actually are analogous to
those separating subspecies elsewhere.

Sometimes it is convenient to recognize species-groups, a systematic
category without nomenclatural status, intermediate between the species
and the subgenus. When there are two groups of species not sharply
separated, including one species whose characters overlap those of each
of the two groups, it would seem most appropriate to recognize only
species-groups instead of subgenera. When, on the other hand, the two
groups of species have mutually exclusive characters and a species with
intermediate characters is unknown, the two groups of species can
conveniently be accorded separate subgeneric rank.


SUBGENERIC VARIATION

A few characters are common to one group of species and other features
are common to a second group. The most striking of these features is the
character of the main fold in the molariform teeth. In one group the
fold transversely crosses the crown of the tooth and in the other it
extends scarcely halfway across. No specimen is intermediate in this
respect. These two groups, furthermore, are separated geographically by
an important barrier, the arid belt that starts in the northeastern
littoral of Brazil (Ceará), and that extends south and southwesterly,
more or less accompanying the São Francisco River in the Plateau, to
about 20° S. _Proechimys_ is thought not to inhabit this arid belt. At
the latitude of 20° S the conditions become more suitable for
_Proechimys_, especially along the rivers which flow eastward, but there
the Plateau is replaced by mountains: the Serra Geral at the west, and
Serra da Mantiqueira at the south; these ranges are bare of forests at
higher elevations. Two groups of species of _Proechimys_ are, therefore,
kept geographically isolated: one group lives in southeastern Brazil,
and the other lives in a large area to the west which starts at 21° S in
Paraguay and Brazil and widens northward and includes, farther west,
central and northern Brazil and all the South American countries
above 21° S, as well as Central America northward to southern Nicaragua.

The two groups which are here treated as subgenera may be designated as
follows:

_Trinomys_--main fold deep: aristiforms well-developed on the rump and
outer thighs; tail no less than 75 per cent of length of head and body;
skull without ridges across the parietals; no conspicuous groove for
transmission of nerve inside infraorbital foramen; molariform teeth
decreasing in size from premolar to third molar; 1 to 3 counterfolds in
the molariform teeth.

_Proechimys_--main fold shallow: aristiforms not developed on rump and
outer thighs; tail less than 75 per cent of length of head and body;
groove for transmission of nerve present in infraorbital foramen of
several subspecies; molariform teeth increasing in size from premolar to
second molar; 2 to 5 counterfolds in molariform teeth.

Most of these characters vary but do not overlap. Subgeneric rank is
here accorded to the two groups of _Proechimys_ characterized
immediately above.

The primary cause of the subgeneric differentiation is thought to have
been geologic changes in the continental area. As already pointed out
(see Paleontology), decreasing humidity in the Central Plateau of Brazil
may have caused a migration southwestward of one or more of the species
along with the forests. Once isolated geographically, the species
probably differentiated at an accelerated rate.

The fact that a much larger number of subspecies occupies the larger
geographic range of the subgenus _Proechimys_ would not be sufficient to
prove that this subgenus, _Proechimys_, is nearer to the primitive group
than _Trinomys_, the subgenus occupying the smaller range with fewer
subspecies. The paleontological evolution of the rodents, however,
consistently points to teeth with a larger number of counterfolds (as
seen in _Proechimys_) as the primitive condition. The extension of the
main fold, tending to set apart one lamina in each upper molariform
tooth, seems to be a specialization; reduction in the size of the head
and body, increase in length of tail and decreasing size of molars
posteriorly also may be specializations. The main point, however, is to
establish if _Trinomys_ is a relic group rather than a "differentiated"
one. If an intermediate form were known which connected _Trinomys_ with
one species of _Proechimys_ more than with another or even if _Trinomys_
itself more closely resembled one of the groups of species of the
subgenus _Proechimys_ than it did another, we would assume that
divergence and selection accounted for the subgeneric variation. The
lack of any such connecting link favors the first idea, namely that
_Trinomys_ differentiated rapidly with the aid of geographic variation.

If _Trinomys_ is, as I am inclined to consider it, the result of
"differentiation," its subgeneric features are to be admitted as "new"
and therefore the most primitive species in the genus should be found in
the subgenus _Proechimys_.

It is a matter of common sense to admit the two groups considered above
as subgenera rather than genera. Since the two structural plans were
established they would, and do, act as different sources of variation.
On the other hand, the morphological differences do not give the two
groups an amount of morphological differences that would justify full
generic rank for each.


SPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS

Most of the described forms in the subgenus were initially named as
distinct full species. More recently, however, in accordance with the
ideas now prevalent in systematic work, many of the named kinds were
reduced to the rank of subspecies. Tate first made a geographic
arrangement (1935:399-400) and later (1939:177-178) provisionally
synonymised several named kinds of _Proechimys_ with _Proechimys_
"_cayennensis cayennensis_." A similar tendency was clearly displayed by
Ellerman (1940:115-122) who allocated 29 names, out of 33 (in the
subgenus, as here understood), to the species _Proechimys guyannensis_
and gave full specific rank to four other named kinds. Osgood (1944)
also had the same viewpoint; that is to say, he appeared to have the
idea that there were only two full species in the subgenus in
Brazil--admitting this orally--and consequently he synonymised some full
species where two or more occurred in the same place, thinking that he
was dealing with individual, rather than specific, differences.
Evidently the number of species in the subgenus cannot be great because
the known kinds show few patterns worthy of specific designation and
therefore the majority of the existing names should be suspected of
having no more than subspecific value. Nevertheless none of the above
writers presented real evidence in support of his arrangement.

Criteria for the recognition of full species are most easily recognized
where two or more different species live together. In the literature,
_P. goeldii_ and _P. "oris"_ were mentioned by Thomas (1912:89) as
having been collected in the same place; _P. mincae_ and _P.
canicollis_, by H. H. Smith (in Allen, 1904:440); _P._ "_leucomystax_,"
from Utiarití, by Miranda Ribeiro (1914:42) and _P._ "_longicaudatus_,"
from the same place, by Allen (1916:569) were other examples. In these,
and other alleged instances of two or more kinds occurring together,
detailed study of the specimens concerned was necessary to learn the
true facts. Also with the opportunity to compare collections from
several different places, new facts emerged. _P. longicaudatus_, as it
was conceived of by Allen, was a composite species, but in one locality,
Utiarití, Ribeiro and Allen actually were dealing with two distinct
species.

The species, or subspecies belonging to different species, living
together are: _goeldii_ and _hyleae_, at Fazenda Paraiso; _goeldii_ and
_riparum_ in Manaus; _boimensis_ and _hyleae_ in Tauarí; _leucomystax_
and _villicauda_ in Utiarití; _mincae_ and _canicollis_ in Bonda;
_gularis_ and _hendeei_ on the banks of Rio Napo ("same trap lines,"
according to P. Hershkovitz, _In Litt._). Study of samples of the above
named pairs of kinds of _Proechimys_ showed the following specific
differences: _goeldii_ is large with narrow aristiforms, has a large and
strongly built skull, with four counterfolds in one or more upper
molars: _hyleae_ is smaller, has wide aristiforms, smaller skull with
less pronounced ridges, and never has more than three counterfolds in
the upper molariform teeth; _riparum_ closely resembles _hyleae_;
_boimensis_ has thin aristiforms, small skull and no more than three
counterfolds in the upper molariform teeth in contrast to _hyleae_,
already discussed; _leucomystax_ closely resembles _boimensis_;
_villicauda_ closely resembles both _hyleae_ and _riparum_; _mincae_ is
similar to _hyleae-riparum-villicauda_; _canicollis_ has the number of
counterfolds in all molars reduced to two; _gularis_ is large, has a
strongly built and ridged skull, some upper molariform teeth with four
counterfolds and wide aristiforms; _hendeei_ closely resembles
_leucomystax_ and _boimensis_.

The evidence obtained from study of specimens where two or more species
occurred together was applied to the remaining samples and the
geographic distribution was worked out. As a result the arrangement
below was made, including all valid kinds already named and those here
newly named from Brazil. The names of kinds I do not consider as
belonging to the subgenus (and genus) are excluded. These are _Echimys
macrourus_ Jentink, not seen, and _Proechimys cayennensis hoplomyoides_
Tate (= genus _Hoplomys_). The application of names is tentative,
however, because the types deposited in Europe have not been seen. An
asterisk denotes the forms not seen by me.

      _Proechimys guyannensis: arabupu, arescens, bolivianus, cherriei,
      chrysaeolus, guairae, o'connelli, guyannensis*, hyleae, leioprimna,
      mincae, nesiotes, ochraceus, oris, poliopus, ribeiroi, riparum,
      trinitatis, urichi, vacillator*, villicauda, warreni._

      _Proechimys longicaudatus: boimensis, brevicauda, elassopus,
      hendeei, leucomystax, longicaudatus, nigrofulvus, pachita,
      rattinus*, roberti, securus, simonsi._

      _Proechimys semispinosus: amphichoricus, burrus, calidior,
      centralis, chiriquinus, colombianus, decumanus, goldmani*,
      gorgonae, gularis, hilda*, ignotus, kermiti, liminalis,
      panamensis, rosa*, rubellus, semispinosus._

      _Proechimys goeldii: goeldii, steerei._

      _Proechimys canicollis._

_Proechimys guyannensis_ appears to be more plastic than any other
species. In size of animal, width of aristiforms, color and number of
counterfolds in the cheekteeth, it shows marked response to variations
in geographic conditions. _Proechimys longicaudatus_ is apparently less
plastic; only the number of counterfolds shows marked variation.
_Proechimys semispinosus_ varies much within its range. _Proechimys
goeldii_ seems to be relatively uniform. _Proechimys canicollis_ shows
relatively little variation throughout its range but probably is
divisible into two or more subspecies.

The primitive _Proechimys_ probably was large with a short tail, narrow
aristiforms, strongly built skull, and five counterfolds in each
molariform tooth. Primitiveness here is inferred from characters which
now are of general occurrence in the whole group as opposed to those
restricted in geographic occurrence.

It is a curious fact that in this genus, populations from small islands
are more primitive than populations on the mainland. Apparently a small
population restricted to a small island tends to revert to the primitive
type. The homozygous condition will tend toward a generalized genotype
and the disappearance of secondary biotypes. _P. i. iheringi_ on the
Island of São Sebastião averages larger, has thinner aristiforms, and a
stronger skull than the same subspecies on the mainland, and the
cheekteeth usually have two and three counterfolds. The same subspecies
on the mainland has no more than two counterfolds. _Proechimys
semispinosus gorgonae_ and _Proechimys semispinosus ignotus_, living on
Gorgona and San José islands, respectively, are both characterized by
large size, short tails, strong and conspicuously ridged skulls, and
cheekteeth frequently with four and five counterfolds. On the mainland,
closely related subspecies, like _P. s. panamensis_, _chiriquinus_ and
_gularis_, far less frequently have four counterfolds in more than one
or two teeth. More striking still is the population-sample of _gularis_
from the island of Llunchi, in the Rio Napo, eastern Ecuador. In it
there is a higher ratio of cheekteeth with four counterfolds than there
is in the samples from the banks of the river.

The two insular forms, _P. s. gorgonae_ and _P. s. ignotus_, referred to
as primitive in the discussion above, have wide aristiforms, which is
contrary to what would be expected in a primitive _Proechimys_.
Supposing, however, as actually seems to be the fact, that narrowness of
the aristiforms depends on an increased number of genes, we deduce that
the population from the mainland, that gave rise to the populations of
the islands, did not have all of the genes necessary to make the
aristiforms narrow. In fact the subspecies known on the mainland, near
the aforementioned islands, have wide aristiforms.

Another point which favors the idea that narrow aristiforms result from
an increased number of genes is that, generally, the aristiforms are
narrow in any species whose geographic range is extensive and relatively
uniform.

_Proechimys goeldii_ is the species which has the largest number of
characters that are judged to be primitive, and it may be the oldest
stock. _P. semispinosus_, _P. longicaudatus_ and _P. guyannensis_ may
have been derived from an early splitting of the genus or they may have
branched off the main stem at different times. _P. canicollis_, however,
seems clearly to be an offshoot of _P. guyannensis_; _canicollis_ shows
greater resemblance to _guyannensis_ than to any other species. _P. g.
vacillator_ is another close relative of _P. guyannensis_ with the
number of counterfolds almost as much reduced as in _P. canicollis_.
Conceivably, _vacillator_ is a full species, but the reduction in number
of counterfolds in the teeth more probably expresses only one extreme of
a gradient, as will be discussed below.


SUBSPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS

In spite of the lack of specimens from areas in which _Proechimys_
certainly occurs, it is evident that the genus has great plasticity and
that the number of subspecies will be greatly increased as additional
material is studied. Only perfunctory examination of samples from
outside the area of Brazil shows me that there are several unnamed
subspecies there. My impression is that Allen's _trinitatis_, of
Trinidad, the genotype of _Proechimys_, will eventually be split.

There are two main lines of subspeciation in _Proechimys guyannensis_.
The one south of the Amazon River includes _P. g. bolivianus_, in
Bolivia, _P. g. villicauda_, and _P. g. ribeiroi_ occurring on the
divide of the headwaters of the Amazon and Parana rivers, in Brazil, and
_P. g. hyleae_ in the lower Tapajoz and _P. g. nesiotes_ in the lower
Tocantins. All six subspecies have a large number of counterfolds in the
molariform teeth. In these six subspecies, p4 has four counterfolds and
the lower molars have three each. Toward the northeastern coast the
number of counterfolds decreases to three in p4 and to two in the lower
molars, as in _P. g. arescens_, _P. g. leioprimna_ and _P. g. oris_.

In northern South America, north of the Amazon River, the subspecies
with the greatest number of counterfolds is _P. guyannensis warreni_
(known from only the Demerara River area); p4 has four counterfolds and
the lower molars have three each. The number decreases in all the
adjacent populations: _P. g. guyannensis_, in the Guianas, _P. g.
trinitatis_, and _P. g. urichi_ (going westward from the Guianas to
Venezuela) have the counterfolds reduced to three in p4, but the lower
molars still have the same number of counterfolds, namely, three,
although there is a tendency for them to coalesce; farther west, on the
coast, the number decreases to three counterfolds in p4 and to only two
in the lower molars as in _P. g. guairae_ and _P. g. mincae_. Subspecies
south of the coast show the same reduction of counterfolds, _P. g.
cherriei_ and _P. g. o'connelli_ being examples; _P. g. ochraceus_ and
_P. g. poliopus_ have the reduction carried to the upper molars, M3
having usually only two counterfolds; _P. g. chrysaeolus_ in the valley
between the Madalena and the Cauca rivers seems to be somewhat isolated
and shows reversion to three counterfolds in the lower molariform teeth;
directly southward of the range of _P. g. warreni_ the number of
counterfolds decreases to three in all lower cheekteeth (population at
Ayan-Tepuy, southern Venezuela), and then to three in p4 and to two in
the lower molars, as in _P. g. arabupu_ on the Brazilian side of Mount
Roraima, and the reduction is extended to the upper molars in _P. g.
vacillator_.

On the north bank of the Amazon, the only population of _P. g. hyleae_
known to me (from Obidos) has four counterfolds in p4 and three in the
lower molars; _P. g. riparum_, from Manaus, also on the north bank of
the Amazon, has three counterfolds in p4 and two counterfolds in the
lower molars. _P. g. hyleae_ occurs also on the south bank of the
Amazon. _P. g. riparum_, therefore, may be the northern part of the
southern cline, instead of the southern end of the northern cline.

The whole picture, as outlined above, may be explained by assuming that
the species _P. guyannensis_ differentiated somewhere on the Central
Plateau of South America, with three counterfolds in each upper
molariform tooth, four counterfolds in the lower premolar and three
counterfolds in the lower molars. The species might have extended its
range to the Guianas and then all the biotypes with reduced number of
counterfolds might have slowly developed by natural selection. The
gradient is, broadly, from subspecies with greater number of
counterfolds in more humid areas, to a gradually lessening number of
counterfolds in less humid areas.

_Proechimys longicaudatus_ is limited in the south to the headwaters of
the Parana River drainage, where the subspecies _P. l. roberti_ and _P.
l. longicaudatus_ are found. The species ranges northward through the
Tapajoz drainage, with _P. l. leucomystax_ in the headwaters and _P. l.
boimensis_ in the lower course. To the northwest and west the species is
represented in Bolivia by _P. l. securus_; _P. l. elassopus_, _P. l.
simonsi_, _P. l. pachita_, and _P. l. hendeei_ occur in Peru and _P. l.
brevicauda_ in Peru and Brazil; and _P. l. nigrofulvus_ occurs in
Ecuador. Again in _P. longicaudatus_ it seems that the number of
counterfolds follows a gradient from more humid areas with four
counterfolds in p4, as seen in _nigrofulvus_, _pachita_, _simonsi_,
_elassopus_ and _brevicauda_, decreasing to three or four in _securus_,
to three in _longicaudatus_, but with m3 having only two counterfolds in
_leucomystax_ and _roberti_. _P. l. boimensis_, widely separated in the
lower Tapajoz (no samples being known from the intervening range) may be
the end of a cline started by _leucomystax_ with only 2 counterfolds in
m3 and ending to the northward with four counterfolds in m3. Over the
same area the counterfolds in p4 increase from 3 to 4.

Of _Proechimys goeldii_ I have had inadequate material but there seems
to be a similar gradient in it which may be traced from _P. g. steerei_
to _P. g. goeldii_. _P. g. steerei_ has four counterfolds in more upper
molars than occurs in the other subspecies.

_Proechimys semispinosus_ has its wide range in the mountainous, western
area of South America, the headwaters of the Amazon drainage and
northward in Central America and the nearby Pacific Islands. In these
populations a gradient may exist in the number of counterfolds which is
varied in every population. The highest number seems to occur in the
populations from northern Peru and Ecuador, decreasing from there in all
directions, except in the Panamanian and Columbian islands. In gross
examination, it seems that the size of the animals increases to the
northwards.


SPECIFIC VARIATION IN THE SUBGENUS TRINOMYS

Some specific characters are duplicated in each of the two subgenera;
that is to say, there are some parallel developments and they give the
common generic stock its biotypical variability. Among these parallel
developments are the width of the aristiforms, the amount of pigment in
the agouti-colored setiforms, and the shape of the nasal bones. Other
characters, however, appear in one subgeneric group and not in the
other. The specific variation will be discussed separately for each
subgenus.

The aristiforms are narrow and soft in _P. dimidiatus_ and in the other
species are wide and stiff, and on the outer thighs and rump some are
light-colored. _P. albispinus_ has the maximum number of light-colored
aristiforms; they are present over the sides and back. This species has,
however, a type of aristiforms unique in the genus--the clavate type.
The tail is longer in _P. iheringi_ and _P. setosus_ than in _P.
dimidiatus_ and _P. albispinus_; the longer type is associated with a
penicillate tip suggesting an adaptation to arboreal habit. The skull
and nasals are longer in _P. dimidiatus_ and _P. iheringi_ than in _P.
setosus_ and _P. albispinus_. In the latter two species the longitudinal
dorsal outline of the skull is conspicuously convex as opposed to
slightly convex in the other two species. The palate is longest in _P.
dimidiatus_ and _P. iheringi_ extending posteriorly to the level of the
second molars; it is slightly shorter in _P. setosus_ and shortest in
_P. albispinus_ where it does not extend behind the level of the first
molars. The incisors are opisthodont in _P. dimidiatus_ and _P.
iheringi_ and orthodont in _P. setosus_ and _P. albispinus_ and even
proodont in one part of the last species.

The molariform teeth have a large number of counterfolds in both _P.
dimidiatus_ and _P. iheringi_, although the number varies but little in
the first species and much in the second. The variation in _P. iheringi_
decreases in populations of increasingly more northern geographic
distribution; in both _P. setosus_ and _P. albispinus_ the number of
counterfolds is greatly reduced; there is only one in most specimens of
_P. albispinus_. The incisive foramen is small and nearly round in _P.
dimidiatus_, larger and elongate in _P. iheringi_, very narrow and
fissurelike in both _P. setosus_ and _P. albispinus_.

The characters of _Trinomys_, as briefly outlined above, seem to be the
result of one original species having split first into four species
which provide a gradient for certain characters. Subsequently one of
these four species, _P. iheringi_, split into six subspecies and
another gradient, parallel to the first, and involving the same
characters, is to be seen.

The interrelationship among the species is evident, not only because
they have the same subgeneric characters, but because the full species
themselves provide successive steps in a stairway of increasing
specialization from _P. dimidiatus_ to _P. albispinus_.

Morphologically _P. dimidiatus_ and _P. iheringi_ are sometimes
difficult to distinguish, especially on the basis of cranial features.
Nevertheless close attention to the small, nearly round, incisive
foramen of _P. dimidiatus_ versus the larger, more elongate foramen in
_P. iheringi_ will permit separation of the two. However, the two
species live in the same place and one is led to infer that there may be
greater differences in their physiology than in their morphology. In
fact Dr. H. W. Laemmert, from the Serviço de Estudos e Pesquisas Sobre a
Febre Amarela in Brazil, informs me that while _P. dimidiatus_ was
highly susceptible to the virus of yellow fever (18 out of 24 with virus
in circulation), _P. iheringi_ showed a lower rate of susceptibility (3
out of 25 with virus in circulation). _P. longicaudatus roberti_,
belonging in the other subgenus, showed no susceptibility at all.

At Teresópolis, Estado do Rio de Janeiro, the two species were found in
two different forests, only a few kilometers apart, but _dimidiatus_
lived at a higher elevation, where the humidity was remarkably higher.
Naturally the plant associations were different in the two forests. This
seeming ecological adaptation of the two kinds of _Proechimys_ may
explain why _P. iheringi_ ranges farther north; the forests to the
northward are less humid.

One of the four species, _P. setosus_, subspecies _elegans_, was used by
Winge (1941:80, 82) as representative of the genus _Proechimys_ when he
was estimating the relationships of that genus. Because _Cercomys_, with
four crests in each of its cheekteeth, was, on other grounds, regarded
by him (_op. cit._: 80) as "... the most primitive genus within the
group.", and because he noted in _P. s. elegans_ 4 crests in P4 and in
some first molars, he concluded that _Proechimys_ was "very closely
related to _Cercomys_." His conclusion seems to be correct, but actually
other species of _Proechimys_ (subgenus _Trinomys_), for example, _P.
dimidiatus_, have four or more crests in each cheektooth, and,
therefore, may be considered as more closely related to _Cercomys_ than
is _P. setosus_. If a large number of crests indicates primitiveness,
_P. dimidiatus_, always with four, is more primitive than any other
species in the subgenus _Trinomys_. Also, the large skull, long hind
foot, short tail and thin aristiforms of _P. dimidiatus_, in my opinion,
are primitive characters.


SUBSPECIFIC VARIATION IN THE SUBGENUS TRINOMYS

One of the species of _Trinomys_, _Proechimys iheringi_, is here
subdivided into six subspecies which show a clinal variation. _P. i.
iheringi_, in the southernmost part of the range of the species (Ilha de
São Sebastião), has three counterfolds in the upper cheekteeth of almost
every young specimen but one of these counterfolds, since it is small,
very shallow, and disappears after little wear, is probably in the
process of disappearance; all lower cheekteeth have two counterfolds or,
rarely, m3 has only one. _P. i. bonafidei_ is the next subspecies
northward, where it was collected at 850 m altitude (Fazenda Bõa Fé).
This subspecies still has two counterfolds in all the upper cheekteeth;
only 3 out of 16 specimens fail to have these counterfolds coalesced in
one or more of the teeth. In the lower cheekteeth the coalescence is
evident in 18 per cent of the specimens. _P. i. gratiosus_, from
Floresta da Caixa Dagua (alt. 750 m), geographically is well removed from
_bonafidei_ (more than two degrees north), and no samples were obtained
from the intervening area. It shows such great reduction in the
counterfolds that the existence of intermediate populations is clearly
suggested. Every upper cheektooth of this subspecies has the two
counterfolds coalesced and in 40 per cent of the specimens M3 has only
one counterfold; in the lower cheekteeth 60 per cent of the specimens
have only one counterfold in m3. _P. i. panema_, occurring approximately
100 kilometers to the northward of _P. i. gratiosus_ (lowland form), has
one counterfold in M3 in only 20 per cent of the specimens but the lower
third molar has only one counterfold in 80 per cent of the specimens. In
_P. i. denigratus_, from about 3 degrees north of the range of _P. i.
panema_, the reduction is proportionately greater: P4 now is the only
upper cheektooth with two counterfolds in every specimen; all molars
tend to have only one; p4 has also two counterfolds but all lower molars
have only one.

The relative size of the tail also varies in a cline from south to
north. Its length is approximately 87 per cent of the length of the head
and body in _P. iheringi_; 88 per cent in _bonafidei_; 99 per cent in
_gratiosus_; 100 per cent in _panema_; and 103 in _denigratus_.

One of the subspecies, _P. i. paratus_, however, seems to be completely
out of the dental cline. It was collected in the near proximity of the
type locality of _P. i. gratiosus_, at an elevation of 120 m lower. This
subspecies has two counterfolds in all molariform teeth and only one of
the two specimens known shows these counterfolds coalesced in P4 and M1.
The sample, 2 specimens, is too small to be trustworthy; hence it is
impossible satisfactorily to account for the break in the clinal
variation. Conceivably two full species are involved, but I prefer at
present to defer decision on this problem until such time as more
evidence is accumulated.

_P. setosus_ is poorly represented, both of the available skins being
faded. Furthermore, no type locality is known for the subspecies _P. s.
setosus_.

_P. albispinus_ has only two known subspecies: _P. a. albispinus_,
living in a region of higher humidity, is slightly the darker and has
subapical zones of the setiforms on the sides Ochraceous-Tawny; _P. a.
sertonius_, living in a much drier region, has the same subapical zone
Ochraceous-Buff. The number of specimens of _P. a. sertonius_ is so few
that no gradient can be detected, even if one exists.




TAXONOMIC CHARACTERS


Size and Proportions of External Parts

Absolute size of head and body, tail, hind-foot and ear are useful in
distinguishing subgenera and subspecies and to some extent in
differentiating species.

The length of head and body is large to medium in _Proechimys_ and
medium to small in _Trinomys_. The tail is long to medium in _Trinomys_
and short in _Proechimys_. The longest tail, 242 mm, is found in _P. i.
denigratus_, and the shortest tail, 123 mm, in _P. g. steerei_. The
relative length of tail also provides gradients or clines.

In every species, males surpass females in average size. Nevertheless,
the largest animals are usually females. How this paradoxal fact is to
be accounted for, I am not sure, but it may be that the animals grow as
long as they live and that females have more chances to survive longer
since the care of the young keeps them closer to shelter.

_Color._--Upper parts vary from Buckthorn Brown to Ochraceous-Buff. Dark
color ordinarily is correlated with an environment of higher degree of
humidity and light color with lower humidity. However, species may be
found in similar conditions of humidity but differing in color.
_Proechimys albispinus albispinus_, for example, a light-colored form,
is found in areas where the rainfall averages 1,000 to 1,500 mm of
annual precipitation, in the isohygra of 80 per cent relative humidity.
These conditions actually are similar to those where _P. dimidiatus_, of
darker color, is found. The subspecies _albispinus_, however, ranges
mostly over a dry area and the fact that it occurs also in a moist area
without appreciable change in color is difficult to explain.

Insular populations are usually darker or richer in color than
corresponding continental populations. On a small island, uniformity of
environment and inbreeding may be responsible for an accumulation of
characters for richness of color.


Pelage

The pelage provides most useful taxonomic characters. Excepting the
vibrissiform hairs, all of the elements of the pelage have a common
feature, the flattened shape. The hair constellation (_cf._ Toldt, 1935)
on the upper and lateral surfaces is composed of hairs of two main
types: _aristiforms_ (guard hairs) and _setiforms_ (over hairs).

The aristiforms are wide, strong, and have the dorsal (= anterior)
margins raised, forming a wide shallow longitudinal groove on the dorsal
face of the hair. The tip is a filament that usually is lacking in
aristiforms which are especially strong. Wear probably removes these
tips. The aristiforms have the bases whitish or grayish and the amount
of pigment gradually increases distally to a dark brown or blackish
shade. On the dorsal and lateral surfaces of the head the aristiforms
are small and narrow but gradually increase in length and width caudad
on the animal. The maximum development is reached in the middorsal
region, from where they decrease in size and number toward the lateral
surfaces or caudad. This decrease in the development of the aristiforms,
however, is not uniformly gradual. Generally, the aristiforms become
increasingly conspicuous in a middorsal band, but they extend to the
sides and onto the outer sides of the thighs; the band narrows rapidly
on the rump. In the subgenus _Trinomys_, where the aristiforms attain
their maximum development, they are still strong and conspicuous on the
rump and sometimes around the base of the tail. In _Proechimys_ the
aristiforms do not extend caudad from the hips. Also, in _Trinomys_,
besides the ordinary lanceolate type, there are some aristiforms on the
dorsal surface with a clavate shape; the base is wide and the distal
part narrow. This parallels the conditions in the pelage of the most
spiny species in the genus _Echimys_, _Echimys chrysurus_
(Lichtenstein).

The recently named subspecies _Proechimys cayennensis hoplomyoides_
Tate, 1939, shows an extraordinary development of the aristiforms on
the back and sides such as occurs in the genus _Hoplomys_. Actually the
small bulla, wide basisphenoid and tooth structure add to the
possibility of _hoplomyoides_ being a true _Hoplomys_, and worn teeth
might have been responsible for the difficulty which Tate had in
allocating the form to the proper genus. However, the narrow braincase
is more nearly like that of _Proechimys_ than that of _Hoplomys_. The
intermediate nature of _hoplomyoides_ argues for including the genus
_Hoplomys_ as a subgenus of _Proechimys_.

Species with narrow aristiforms have a rather soft and flexible pelage,
while those with wide aristiforms have harsh, spiny pelage. The
aristiforms vary in width from 0.45 to 1.3 mm, depending upon the
species or subspecies.

Animals with narrow aristiforms tend to have a more or less uniform
coloration throughout the dorsal parts. The blackish distal parts of the
aristiforms regularly interline the ground color made by the subapical
zone of the setiforms. If, on the contrary, wide aristiforms occur, the
dorsal surface is conspicuously marked by the wide blackish lines among
spots of color formed by the subapical zones of the setiforms. No clinal
variation was detected in width of aristiforms but geographic variation
in width was noted; for example, the subspecies of _P. iheringi_ differ
in this respect.

The setiforms are narrow and flattened but are without pronouncedly
raised margins. The setiforms are usually bicolored on the dorsal and
lateral surfaces of the animals, with a subapical zone of some
reddish-brown color, like Ochraceous-Orange or Ochraceous-Buff. They are
whitish or gray on the basal parts and gradually blacken toward the tip,
but have a reddish subapical zone. Common exceptions to this pattern are
setiforms without subapical zones; these appear on the dorsal surface
among setiforms which are normal in possessing distinctive subapical
zones. Also there are setiforms without blackened tips on the lateral
surfaces. Due to their relative abundance and subapical color, these
setiforms are responsible for the dominant color on the upper parts.
Like the aristiforms, they are longer and wider in the middorsal region
of the animal and are gradually less developed on the remainder of the
upper parts. Actually there is more than one type of setiform in the
hair constellation; they vary in length, width and color. Attention was
not given, however, to every type of setiform.

The ventral surface of the body and the inner sides of the legs are
uniformly covered by short setiforms, thinner and more sparsely
distributed on the inner side of the legs. These setiforms are usually
uniformly white in color or, sometimes, the distal parts are buff or
more richly colored.

Vibrissiforms are scattered on the dorsal and lateral surfaces of the
body, and in penicillate arrangements on the head. They are longer than
the pelage proper, have a nearly circular cross-section and are blackish
in color.


Skull

The absolute size of the skull is proportionate to bulk of the body. The
supraorbital and parietal ridges are especially developed in the _P.
semispinosus_ group, where they extend across the parietals to the
interparietals. In all members of the subgenus _Proechimys_, these
ridges extend onto the parietal region. In _Trinomys_, however, they do
not extend so far posteriorly as the parietal, but only onto the
squamosal.

The rostrum varies from slender to stout. Elongate rostra are common in
_Proechimys_; _Trinomys_ has a short blunt rostrum.

The infraorbital foramen commonly has a ventral groove for nerve
transmission in many forms of _Proechimys_ but _Trinomys_ almost always
lacks this groove. Presence or absence of the groove is a subspecific
character in the subgenus _Proechimys_.

The jugals are dorso-ventrally wide in _Trinomys_ except in the species
_P. setosus_. In _Proechimys_ a dorso-ventrally narrow jugal is the
rule, but _P. canicollis_ has an especially wide jugal. A postorbital
process appears on the jugo-squamosal suture and is here called
postorbital process of the zygoma. In _Proechimys_ it is more or less
weakly developed and shows no variation of systematic worth. In
_Trinomys_, on the other hand, this process varies in a clinal way (_P.
iheringi_) and stages of the gradient characterize populations of
subspecific rank.

Linear and spatulate shape of the humular process of the
pterygoid constituted specific characters for Thomas, but there is so
much individual variation in the shape of this process in almost every
population that it has not been used in the present account.

The mesopterygoid (interpterygoid) fossa in almost every specimen
extends anteriorly to the level of M1 or M2 in _Trinomys_, and to M3 in
_Proechimys_. Exceptions may occur, as in _P. hendeei_, where the fossa
extends to the level of M2.


Incisive Foramen

The shape and dimensions of the incisive foramen long have been
recognized as providing specific characters. Large size of the foramen
is probably correlated with the requirement for a large amount of
moisture reaching Jacobson's organ in the nasopalatine space; the
moistening of the sensory epithelium is certainly involved. There seems
to be a certain correlation between small size of the incisive foramen
and high degree of humidity in the environment. Shapes and dimensions of
the foramen appear as simple or multiple biotypes and provide characters
which can be employed to differentiate subspecies, species and even
subgenera. Usually a character, say a general shape, occurs in nearly
all populations of a given subspecies but the particular shape seems to
be more closely correlated with ecological conditions, especially
humidity. Animals which live far away from large rivers usually have
larger foramina than animals which live close to rivers.

Both the premaxilla and the maxilla develop processes which form a
sheath for the vomer. This vomerine sheath forms a bridge which
longitudinally crosses the incisive foramen; the structure of this
bridge varies widely. Sometimes the maxillary part is not developed and
the sheath is incomplete posteriorly; sometimes this maxillary part is
very slender and merely touches the premaxillary part. The premaxillary
part, however, is always well developed.


Teeth

Considered by itself the variation in the tooth pattern can lead to
erroneous conclusions as to differentiation of species, because the
number of folds on the occlusal face of a tooth and the depth of certain
folds may be subject to great individual variation as shown by
examination of more than one large series of specimens of the same kind,
age and sex from a single locality. Also there are geographic gradients
or clines, in number of folds. Nevertheless the variation in number of
folds, when measured at sufficient intervals along a cline, may provide
quantitative characters useful in differentiating subspecies.

[Illustration: FIGS. 2-17. Second left upper molar of the two subgenera
_Proechimys_ and _Trinomys_. All × 8. Anterior border of tooth is at the
top of each figure (Nos. 9 and 17 excepted). Note especially that main
fold is short in _Proechimys_ and long in _Trinomys_.

    FIGS. 2-9. _Proechimys_ (_Proechimys_) _semispinosus liminalis_,
    female, MN no. 6243, Rio Quichito. Fig. 2, unworn crown. Figs. 3-8,
    cross sections at 0.5 mm. intervals, showing changes in the main fold
    and counterfolds at increasing depths as the tooth was ground down.
    Fig. 8 is 3 mm. below surface shown in fig. 2. Fig. 9, posterior view
    with proximal end of the tooth open showing basal ends of folds.
    Later in life the proximal end closes and three roots are formed.

    FIGS. 10-17. _Proechimys_ (_Trinomys_) _iheringi denigratus_, female,
    SEPFA no. 17060, Mata do Ribeirão da Fortuna. Figs. 10-16
    corresponding to figs. 2-8. Fig. 17, posterioventral view with
    proximal end of the tooth open and part of walls cut away, showing
    basal ends of folds. Later in life, as in _Proechimys_, the proximal
    end closes and three roots are formed. ]

The main fold involves both the occlusal face of the tooth and the side
wall. The counterfolds, which are smaller counterparts of the main fold,
in most instances also implicate the wall of the tooth opposite to that
marked by the main fold, but are to be seen mostly on only the occlusal
face of the tooth. Unerupted teeth with the crowns unworn and other
teeth which had barely broken through the gums were ground down to
permit the making of drawings of the surfaces at different levels. This
study revealed that the main fold is deepest in the wall of the tooth.
The development of the main fold varies in two different ways: in all
samples from southeastern and eastern Brazil it is strongly developed,
deeply grooves the tooth through its crown and, in younger individuals,
completely divides the occlusal surface of the tooth. As use wears down
the crown, the main fold soon becomes separated from the opposite wall
and then gradually shortens toward its basal portion. In the other type,
common to animals of all the remaining part of the range of the genus,
the main fold is rather short, never reaching the opposite wall. In this
case, however, one of the counterfolds usually appears almost opposite
the main fold in such a way that in non-erupted or just-erupted teeth
the main fold and one counterfold may be connected by a shallow groove
that may give the impression of extension of the main fold and,
therefore, lead to false interpretations. Closer examination shows that
the counterfold which apparently meets the main fold is really situated
anteriorly or posteriorly to it, in upper or lower teeth respectively.
One subspecies in the subgenus _Trinomys_ differs from the general
characteristics of the subgenus in sometimes showing a small main fold
in P4 whereas it is large in all other cheekteeth. The structural
differences here mentioned in the main fold were never before
recognized. Therefore, the meaning of "quadrilaminate" pattern, "three
outer folds" or "three inner folds" (of authors) is not consistent
insofar as the two groups are concerned.

Writers have more or less tacitly admitted three as the usual number of
counterfolds present in the upper molariform teeth. Ellerman, for
example (1940:117), states: "Upper cheekteeth normally with three outer
and one inner folds each, these soon becoming isolated as islands. A few
species, which will be discussed below, vary slightly in pattern."
Thomas (1921:140) erected the subgenus _Trinomys_ on the basis of the
upper molariform teeth having only three laminae. Actually a meticulous
study of widely varying samples shows that the number of counterfolds
may vary from _one_ to _five_, the usual number being three or four. One
of the most important facts to record on this subject is that young
specimens with slightly worn molariform teeth are more apt than either
adult or younger specimens to show the maximum number of counterfolds.
Usually nonworn teeth show rounded crests and valleys of different
depth. For example, it is common to see one continuous groove giving the
impression of a main fold crossing the occlusal surface transversely.
The slightest wear of the occlusal surface, however, shows that really
there are two valleys instead of one. The two are the main fold and one
counterfold. In this case, it would be easy to confuse the two types of
teeth, one with the main fold short and the other with the main fold
extending almost all the way across the occlusal surface.

Some of the counterfolds are especially shallow and tend to disappear in
an early stage of wear, and adult individuals may have these folds
completely worn away. Advanced wear usually develops a cuplike occlusal
surface with only the remains of the main fold and also remains of one
or more counterfolds represented by small enamel islands (Figs. 2 to
17). In the form _Proechimys iheringi iheringi_, for example, every
tooth shows three counterfolds in the upper molariform teeth of
individuals in which the wear is not advanced. This number, however, is
less in all or part of the molariform teeth of older individuals.

Adjacent counterfolds may appear to be coalesced in many instances.
Coalescence is more likely to be seen in species where a wider variation
in the number of the counterfolds is involved and it appears as a
gradient in the reduction of the number of counterfolds.

Of great importance, as a general feature of molariform teeth, is the
relative size as related to the geographical distribution, showing,
again, a natural division in the genus. In all forms of southeastern
Brazil the premolars are larger than the first molars, the first molars
are larger than the second molars, and the second molars are larger than
the third molars. The forms from central and northern Bahia, Brazil,
have the molariform teeth more or less the same size. The forms from the
remaining part of the area occupied by the genus have premolars smaller
than the first molars, the first molars smaller than the second molars,
but the second molars larger than third ones.




HABITS


_P. dimidiatus_ was studied in the field and laboratory. _P. dimidiatus_
in captivity showed regular diurnal activity, coming out of the nest for
food at intervals. Individuals were fed a cereal mixture and nuts of
small size. The animals usually buried the nuts in the sand of the outer
cage. While holding the nut with the mouth and front feet, the animal
patted the sand rapidly, thus burying the nut, and it then pushed more
sand over the place with the front feet.

Sometimes the emergence from the nest is followed by a long yawning and
stretching ceremony. The animal spreads the fore and hind legs widely
apart, while the back is curved down and the head and tail turn upward.
Then one of the hind legs is stretched backward and, at the same time,
the mouth is opened widely and the tail is moved in an undulatory
fashion. The operation may be repeated using the other legs, or not.

_P. dimidiatus_ was regularly found in climax forest. The best shelter
and nesting ground was usually under boulders, commonly not farther than
10 meters from water. The entrance to the nest was kept clean. No more
than two adult animals (male and female) were captured in the same
shelter, and only a few times were young captured in the same place with
adults. Nesting places were located also at the bases of trees and near
fallen logs where litter accumulates.

Records of animals kept in captivity show that the species _dimidiatus_
survives more than two years. Specimen MN no. 5448 [M] was adult when
captured by the Serviços de Estudos e Pesquisas sobre a Febre Amarela on
December 5, 1938, and died on January 17, 1942. Therefore, it lived for
more than 1,139 days.

_Proechimys dimidiatus_, in Rio de Janeiro, as well as _P. i. bonafidei_
and _P. i. iheringi_ which live in the same region, were found breeding
from September to November and from March to May. _Proechimys
longicaudatus roberti_, in Anapolis, Goiaz, was found breeding from July
to November and from January to March. _P. g. hyleae_ and _P. g.
leioprimna_ in the lower Tapajoz and lower Tocantins rivers, Pará, were
found breeding in January.

It seems that in the Central Plateau and southeastern Brazil,
_Proechimys_ has two litters per year, one in the early spring and a
second in the late summer. The number of young per litter varies from 1
to 5, although 2 is the usual number.




CHANGES WITH AGE


_Juveniles._--The animals are born with a thick pelage of thin
aristiforms and thin setiforms. The color is uniformly blackish brown.
The nose, hands, feet, ears and tail are pinkish; P4 and M1 are already
erupted and the second molars are included in the bony alveoli. The
incisors are orthodont; the rostrum is short and the braincase is wide.
The posterior part of the skull is greatly curved dorsally. No change is
noticed in the pelage before the second molars erupt and become
functional.

_Adolescents._--As soon as the second molars become functional, the
pelage starts molting on the back. The thin aristiforms are still in
place but the aristiforms of the adult pelage may be noticed growing
under them in an oval patch which extends from behind the shoulders
caudad to the hips. At that age the first, agouti-colored aristiforms
appear on the mystacial region, immediately behind the vibrissiforms.
The rostrum gradually lengthens and the braincase appears to become less
inflated.

By the time the third molars erupt, the aristiforms start showing among
the setiforms which are now changing to agouti color in the same area on
the back, while the thin aristiforms of the juvenal stage disappear. The
agouti setiforms are appearing also posteriorly from the mystacial
region to the sides of the head and neck and, at the same time, on the
frontal region. The patch of glossy aristiforms and setiforms on the
back is sharply differentiated from the dull juvenal pelage of the sides
and rump. In a later stage the area of agouti setiforms on the sides of
the neck extends to the outer sides of the arms and finally reaches the
area on the back where the agouti setiforms were already developed.

_Adults._--When the third molars become functional, the agouti setiforms
are in place except for those on the upper sides of the neck. The
aristiforms have now extended over their normal area of distribution. As
soon as the third molars show wear, the premolars and first molars have
the counterfolds isolated in the occlusal surfaces as enamel islands.
Wearing gradually isolates all counterfolds.

_Senile_ individuals.--Progression of wear soon eliminates the signs of
the shallowest counterfolds from the occlusal surface and finally the
tooth is reduced to a short crown with a cuplike occlusal surface
completely filled with dentine. Only the main fold usually remains; it
is more or less reduced in size.

From the records of the Serviços de Estudos e Pesquisas sobre a Febre
Amarela, the following data for males of _Proechimys longicaudatus
roberti_ were obtained:

  ======================+=========+==========+========+=========+=======
                        | Number  |          | Length |         | Length
              AGE       |   of    |  Weight  | of head|  Length |   of
                        | cheek-  | in grams |  and   | of tail |  hind
                        | teeth   |          |  body  |         |  foot
  ----------------------+---------+----------+--------+---------+-------
  One day old           |    2    |    20.5  |    70  |     53  |   24
  17 days old           |    2    |    26.0  |   110  |     60  |   28
  Juvenile              |    2    |    85.0  |   150  |    105  |   39
  Adolescent            |    3    |   115.0  |   175  |    120  |   45
  Adolescent (older)    |    3    |   180.0  |   195  |    135  |   45
  Adult                 |    4    |   200.0  |   223  |    158  |   48
  Senile individual     |    4    |   360.0  |   230  |    170  |   48
  ----------------------+---------+----------+--------+---------+-------

The weights and measurements (except for one- and 17-day-old animals)
represent averages of specimens of the different ages.


Genus =Proechimys= J. A. Allen

_Genotype._--_Echimys trinitatis_ Allen and Chapman, by original
designation.

      _Proechimys_ Allen and Chapman, 26 December 1899, Bull. Amer. Mus.
      Nat. Hist., 12(20):264, orig. description; Tate, 1935, Bull. Amer.
      Mus. Nat. Hist., 68(5):398; Ellerman, 1940, The families and genera
      of living rodents, Brit. Mus. (Nat. Hist.), 1:115.

      _General characters._--Muriform echimyids of medium size; pelage
      with flattened and lanceolate and sometimes clavate aristiforms,
      varying greatly in width and distributed over most of the dorsal
      surface from shoulders to hips or base of tail; setiforms also
      flattened, evenly distributed throughout; entire ventral surface
      and inner sides of legs white or, rarely, invaded by some buffy
      color; tail shorter than, equal to, or slightly longer than, head
      and body, bicolored and with a few bristles between scales,
      sometimes heavily penicillated; feet long and narrow; pollex
      rudimentary; hallux shorter than fifth toe; ears wide and long;
      mammae 2-1=6.

      _Skull._--Generally elongate and strongly built, with supraorbital
      ridges well developed, frequently extending across parietals
      toward occipital region; zygomatic arches variable in depth,
      always with postorbital process; infraorbital foramen with or
      without lower groove for transmission of nerve; incisive foramen
      usually large; vomerine sheath complete or incomplete;
      mesopterygoid fossa extending forward at least to plane of third
      molars; bullae large; angular process of mandible turned upward.

[Illustration: FIGS. 18-21. Occlusal views of the upper left and lower
right molariform teeth of the two subgenera of the genus _Proechimys_.
Anterior end of the tooth row at the top of drawing. All × 6.

    FIGS. 18-19. _Proechimys_ (_Proechimys_) _goeldii steerei_, sex ?,
    USNM no. 105537, "Hyutanaham." Upper teeth at left (fig. 18).

    FIGS. 20-21. _Proechimys_ (_Trinomys_) _dimidiatus_, male, MN no.
    6256, Pedra Branca. ]

     _Teeth._--Incisors opisthodont, orthodont or proodont, not grooved;
     upper molariform teeth with a main internal fold and one to five
     external counterfolds which usually appear as enamel islands in
     worn teeth, these counterfolds barely implicating the lateral wall;
     lower molariform teeth with folds as in the upper molariform teeth
     except that they are reversed and the number of internal
     counterfolds is usually fewer in the molars.




ARTIFICIAL KEY TO THE SUBGENERA AND SPECIES


  1. (_a_) Tail less than 90 per cent of head and body; aristiforms
         not evident on outer thighs and rump; skull
         with ridges across parietals; size of upper cheekteeth
         increasing from P4 to M2; main fold small.
                                          subgenus PROECHIMYS,         2

     (_b_) Tail 90 per cent or more of head and body; aristiforms
         evident on outer thighs and rump; skull with
         no ridges across parietals; size of upper cheekteeth
         decreasing from P4 to M3; main fold large.
                                          subgenus TRINOMYS,           5

  2. (_a_) One or more upper molars with four counterfolds             3
     (_b_) Upper molars with no more than three counterfolds,          4

  3. (_a_) Aristiforms wide (more than 0.7 mm).  _P. semispinosus_, p. 342
     (_b_) Aristiforms narrow (less than 0.7 mm) _P. goeldii_,      p. 338

  4. (_a_) Aristiforms wide (0.9 mm or more), or narrow (0.6
         to 0.7 mm) but then with only two counterfolds in
         each lower molar                      _P. guyannensis_,    p. 355
     (_b_) Aristiforms narrow (0.5 to 0.65 mm) but with one or
         more lower molars having three counterfolds.
                                               _P. longicaudatus_,  p. 346

  5. (_a_) Aristiforms narrow (0.5 mm) and limber; no differentiated
         light-colored aristiforms on outer thighs and
         rump; incisive foramen short and widest posteriorly
                                               _P. dimidiatus_,     p. 371
     (_b_) Aristiforms 0.6 mm or more and stiff; differentiated
         light-colored aristiforms on outer thighs and rump;
         incisive foramen elongated and constricted posteriorly        6

  6. (_a_) Skull large, more than 50 mm in total length, incisors
         opisthodont                           _P. iheringi_,       p. 373
     (_b_) Skull small, less than 49 mm in total length, incisors
         orthodont or proodont                                         7

  7. (_a_) No clavate aristiforms, tail with white tip,
                                               _P. setosus_,        p. 384
     (_b_) Clavate aristiforms among the ordinary ones, tail
         without white tip                     _P. albispinus_,     p. 388

[Illustration: FIG. 22. Map showing the distribution of the two
subgenera of the genus _Proechimys_.]

[Illustration: FIG. 23. Map showing the geographic ranges of four
species of the genus _Proechimys_.]

[Illustration: FIG. 24. Map showing the geographic ranges of four
species of the genus _Proechimys_.]


Subgenus =Proechimys= J. A. Allen


      _General characters._--Pelage with lanceolate aristiforms limited
      to an area on the dorsal surface between the shoulders and the
      hips; length of tail less than 90 per cent of length of head and
      body; skull with conspicuous ridges; extension of supraorbital
      ridges always evident on parietals; infraorbital foramen usually
      with separate groove for transmission of nerve; palate usually
      extended posteriorly as far as third molars; incisors opisthodont;
      molariform teeth with a small main fold, never extended
      transversely to opposite wall in occlusal surface of tooth; usually
      one counterfold anterior to main fold in upper molariform teeth and
      posterior to main fold in lower molariform teeth; premolars usually
      smaller than first molars, first molars smaller than second molars
      but second molars larger than third molars.


=Proechimys goeldii= Thomas

      _General characters._--Size large; tail short; aristiforms narrow
      and soft, usually concealed in pelage by setiforms; general color
      of upper parts some tint of orange, gradually becoming lighter on
      sides with no conspicuous, dark longitudinal band on back; feet
      dark; ventral surface of body and inner side of legs white but
      sometimes with some buff locally; skull broad and strongly built
      but not conspicuously ridged; zygomatic expanse great and rostrum
      not elongate; incisive foramen narrow; bullae large and inflated;
      upper molariform teeth with three to four counterfolds, M3
      ordinarily with four; lower premolars with four, and molars with
      three, counterfolds.


=Proechimys goeldii steerei= Goldman

      _Proechimys steerei_ Goldman, Proc. Biol. Soc. Washington, 24:238,
      28 November 1911 (original description); Goldman, 1912, Proc. Biol.
      Soc. Washington, 25:186; Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119; Osgood, 1944, Zool. Ser.
      Field Mus. Nat. Hist., 29(13):204.

      _Type locality._--Hyutanaham, Upper Purus, _Lábrea_, Amazonas,
      Brazil. _Type:_ United States National Museum, no. 105535, adult
      male; collected in 1901 by Prof. J. B. Steere.

      _Range._--Known only from the type locality and Porto Velho.

      _Diagnosis._--Upper parts Mars Orange on back, grading to
      Ochraceous-Tawny on sides; zygomatic breadth narrow; nasals short;
      incisive foramen narrow and short; vomerine sheath complete and
      thick; upper molars usually with four counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Grayish basally,
      gradually blackening toward tip; total length, 16 to 19 mm;
      maximum width, 0.5 mm. _Setiforms on middorsal region_: Grayish on
      basal third, gradually blackening toward tip but interrupted by a
      Mars Orange, subapical zone 1.5 mm long; total length, 16 to 19
      mm; maximum width, 0.06 mm. _Setiforms on outer thighs_: Whitish
      basally, gradually blackening toward tip but interrupted by Orange
      Rufous or Ochraceous-Tawny, subapical zone; total length, 14 to 16
      mm; maximum width, 0.05 mm.


[Illustration: FIGS. 25, 27. _Proechimys goeldii steerei_, sex ?,
"Hyutanaham," USNM no. 105537. × 1.]

[Illustration: FIGS. 26, 28. _Proechimys goeldii goeldii_, female, AMNH
no. 37488. × 1.]

[Illustration: FIGS. 29, 30. _Proechimys goeldii steerei_, sex ?, USNM
no. 105537, "Hyutanaham." × 1.]

[Illustration: FIGS. 31, 32. _Proechimys goeldii goeldii_, female, AMNH
no. 37488, Fazenda Paraiso. × 1.]

      _Skull._--Large and strong; rostrum rather pointed posteriorly;
      supraorbital ridges not much expanded and extending across
      anterior half of parietals; infraorbital foramen without groove
      for transmission of nerve, or groove obsolete; zygomatic arches
      slender; postorbital process of zygoma involving mostly squamosal;
      incisive foramen short and narrow (4.5 × 2.5 mm) with margins
      almost parallel or tapering gradually caudad and extending toward
      palate as ridges; posterior margin of incisive foramen
      approximately 2.5 mm anterior to premolars; vomerine sheath
      complete, with both elements well-developed; mesopterygoid fossa
      never extending anterior to middle of M3; bullae large, well
      inflated and with shallow grooves.

      _Teeth._--Upper molariform teeth: P4 with three counterfolds;
      upper molars with four counterfolds each or, less commonly, three.
      Lower premolars with four counterfolds; lower molars with three
      each.

      _Comparisons._--From _P. g. goeldii_, _steerei_ differs in: Back
      and sides with more reddish; narrower interorbitally and across
      zygomata; palatilar length less and nasals shorter; maxillary part
      of vomerine sheath thicker; usually four instead of three
      counterfolds in M3.

_Remarks._--This subspecies is clearly related to _P. goeldii_. One
skull from Porto Velho, Rio Madeira, _Guaporé_, Brazil (CNHM no. 21558)
may belong to an unnamed subspecies but is provisionally included here.

In the field notes of Professor Joseph Beal Steere, an entry for no. 72
reads: "Big white bellied wood rats x two young found in nest of grass
on the ground with the two young--_much darker_ young female." No. 77 in
his field notes corresponds to the type specimen.

      _Specimens examined._--Total number, 4, from Brazil, as follows:
      Amazonas. _Lábrea_, Hyutanaham, 3 (USNM); Territ. Guaporé, Porto
      Velho, 1 (CNHM).


=Proechimys goeldii goeldii= Thomas

      _Proechimys goeldii_ Thomas, June 1905, Ann. Mag. Nat. Hist., 15
      (ser. 7):587, (orig. descr.); Thomas, 1912, Ann. Mag. Nat. Hist., 9
      (ser. 8):89; Thomas, 1920, Ann. Mag. Nat. Hist., 6 (ser. 9):277,
      Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400; Osgood, 1944,
      Zool. Ser. Field Mus. Nat. Hist., 29(13):199.

      _Proechimys cayennensis goeldii_, Ellerman, 1940, The families and
      genera of living rodents, Brit. Mus. (Nat. Hist.), 1:121.

      _Type locality._--Santarem, _Santarem_, Pará, Brazil. Type: British
      Museum (Nat. Hist.), no. 5.1.25.6, adult female; presented by Dr.
      E. A. Goeldi.

      _Range._--Margins of the Amazon, between Jamundá and Tapajoz
      rivers.

      _Diagnosis._--Upper parts Ochraceous-Tawny; wide across zygomata;
      nasals of moderate length; incisive foramen long and narrow;
      vomerine sheath complete but maxillary part slender; first and
      second upper molars with four counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally and
      gradually blackening toward tip which is extended as long, thin
      filament; total length, 22 to 24 mm; maximum width, 0.5 mm.
      _Setiforms on middorsal region_: Gray basally, gradually
      blackening toward tip but interrupted by Ochraceous-Tawny,
      subapical zone 3.3 mm long; total length, 19 to 21 mm; maximum
      width, 0.06 mm. _Setiforms on outer thighs_: Whitish basally,
      gradually blackening toward tip but interrupted by
      Ochraceous-Tawny, subapical zone 3 mm long; total length 14 to 16
      mm; maximum width, 0.04 mm.

      _Skull._--Large and strong; nasals pointed posteriorly;
      supraorbital ridges moderately developed and extended caudad
      across anterior third of parietals; zygomatic arches strong;
      postorbital process of zygoma involving mostly squamosal; incisive
      foramen elongate and narrow (5 to 6.5 x 2.3 mm) with margins more
      or less parallel and raised to form ridges which extend posteriorly
      to within 3 mm of plane of premolars; vomerine sheath complete,
      with maxillary part thin and extended caudad as medial crest;
      mesopterygoid fossa extending forward as far as posterior faces
      of second molars or slightly short thereof; bullae large and
      inflated.

      _Teeth._--Molariform teeth large, P4-M3 averaging more than 9 mm
      in length. Upper molariform teeth: P4 and M3 with three
      counterfolds; M1 and M2 with four counterfolds each. In lower
      teeth, p4 with four counterfolds and each molar with three
      counterfolds.

      _Comparisons._--Differences from _P. g. steerei_ are given in the
      account of that subspecies.

_Remarks._--Specimens from the type locality were not available.
Specimens from Fazenda Paraiso, Faro, were relied upon as representative
of the subspecies. These agree with the type according to Thomas
(1912:89). However, the skin of the type was changed in color by
preservative (Thomas, 1905:587) and the best skin he saw was from Faro
(1912:89).

Thomas (1920:277) applied the name _goeldii_ also to specimens from
Manacaparú, a place a short distance above Manaus on the Solimões
(Amazon) River and from Acajutuba, near Manaus, on the Negro River. In
referring to these specimens (2 from Manacaparú and 2 from Acajutuba)
Thomas (_loc. cit._) said "Five molar laminae are frequently, if not
invariably, present among these specimens." He did not, however, mention
whether or not the number of laminae was constant in both M2 and M3. One
specimen from Acajutuba, in the collection of Museu Nacional (MN no.
1973 [M]), actually has five laminae in M3, but the specimens in the
American Museum from Faro agree absolutely with Thomas' original
description of _goeldii_.

Osgood (1944:199) doubted that _goeldii_ was a valid species. Evidence
that Osgood's doubt was unjustified is furnished by the fact that Thomas
(1912:89) pointed out that his specimen from Faro agrees with the type.
Likewise, my two specimens from Faro agree with the type insofar as it
has been described. Thomas (1912:89) mentioned two additional skulls
from the type locality which, he stated, agree with the type which was
received from the Museu Goeldi, Pará.

      _Specimens examined._--Total number, 4, from Brazil as follows:
      Pará, _Faro_, Faro, Fazenda Paraiso, 2 (AMNH); Amazonas, _Manaus_,
      Manaus, 1 skull (AMNH); Amazonas, _Manaus_, Acajutuba, 1 (MN).

      _Additional records._--Total number, 7 (British Museum), from
      Brazil, as follows: Pará, _Santarem_, Santarem (Thomas, 1912:89;
      1920:277), 3; Amazonas, _Manaus_, Acajutuba (Thomas, 1920:277), 2;
      _Manacaparú_, Manacaparú (Thomas, 1920:277), 2.


=Proechimys semispinosus= (Tomes)

[Illustration: FIGS. 33, 36. _Proechimys semispinosus liminalis_,
female, MN no. 6253, Rio Quichito. Type. × 1.]

[Illustration: FIGS. 34, 37. _Proechimys semispinosus amphichoricus_,
male, AMNH no. 77020, Mount Duida. Type. × 1.]

[Illustration: FIGS. 35, 38. _Proechimys semispinosus kermiti_, female,
AMNH no. 37124, Lower Rio Solimões. Type. × 1.2 (from photograph).]

      _General characters._--Size large; tail short and hairy;
      aristiforms wide and stiff, especially well-developed on back;
      general color on upper parts some shade of ochraceous, usually much
      darker on back and forming a conspicuous dorsal band; feet dark;
      ventral surfaces and inner sides of legs white; skull elongate and
      strong with ridges well developed; incisive foramen long and
      narrow; bullae large; usually four counterfolds in M3 and M2;
      usually three but sometimes four counterfolds in M1 and even P4;
      lower premolar with four and lower molars with three counterfolds.

[Illustration: FIGS. 39, 40. _Proechimys semispinosus liminalis_,
female, MN no. 6253, Rio Quichito. Type. × 1.]

[Illustration: FIGS. 41, 42. _Proechimys semispinosus amphichoricus_,
male, AMNH no. 77020, Mount Duida. Type. × 1.]

[Illustration: FIGS. 43, 44. _Proechimys semispinosus kermiti_, female,
AMNH no. 37124, Lower Rio Solimões. Type. × 1.2 (from photograph).]


=Proechimys semispinosus liminalis= subspecies nova

      _Type locality._--Rio Quichito, affluent from the south of the
      Javarí River, near _Benjamin Constant_, Benjamin Constant,
      Amazonas, Brazil. _Type_: Museu Nacional, no. 6253, adult female,
      collected in August, 1942, by E. Parko.

      _Range._--Known only from the type locality.

      _Diagnosis._--Color uniformly dark, setiforms marked with
      Ochraceous-Tawny; skull wide across zygomata; nasals short;
      prepalatilar part of skull long; incisive foramen long and narrow;
      vomerine sheath incomplete or complete; M2 and M3 almost always
      with four counterfolds; M1 more rarely with four counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip which is generally extended as a
      filament; total length, 21 to 23 mm; maximum width, 0.9 to 1 mm.
      _Setiforms on middorsal region_: Gray basally, gradually
      blackening toward tip but interrupted by Ochraceous-Tawny,
      subapical zone 3 mm long; total length, 22 to 24 mm; maximum
      width, 0.06 mm. _Setiforms on outer thighs_: Whitish basally,
      gradually blackening toward tip but interrupted by Ochraceous-Buff,
      subapical zone 2.5 mm long; total length, 13 to 15 mm; maximum
      width, 0.08 mm; some with gray base, blackening gradually toward
      tip, without any subapical zone; some with Light Ochraceous-Tawny,
      subapical zone.

      _Skull._--Large and strongly built throughout; supraorbital ridges
      expanded and thick, extending, in old specimens, across parietals
      to anterior angles of interparietals; interparietal ridges always
      conspicuous; rostrum elongated; nasals blunt posteriorly;
      zygomatic arches strong; infraorbital foramen with
      weakly-developed groove for transmission of nerve; postorbital
      process of zygoma involving mostly squamosal; incisive foramen
      averaging 6 x 2.7 mm, widest in middle part and posteriorly
      constricted, with raised margins which do not extend across
      maxillae as ridges; posterior margin of incisive foramen
      approximately 1.5 mm anterior to plane of premolars; vomerine
      sheath incomplete or, sometimes, complete but always with
      maxillary part slender; mesopterygoid fossa not extending forward
      past centers of third molars; bullae moderately developed.

      _Teeth._--Upper molariform teeth: P4 always with three
      counterfolds; M1 with three counterfolds in 9 of 10 specimens and
      four counterfolds in remainder; M2 with four counterfolds in 7
      specimens, three counterfolds in remainder; M3 with four
      counterfolds in 6 specimens, three counterfolds in remainder.
      Lower premolar always with four, and molars with three,
      counterfolds.

      _Comparisons._--From _P. s. semispinosus_, _liminalis_ differs in:
      darker color; wider aristiforms; greater percentage of upper
      molars with four counterfolds. From _P. s. amphichoricus_,
      _liminalis_ differs in: lighter upper parts of almost uniform
      color instead of with conspicuous, blackish, middorsal,
      longitudinal band; more strongly built skull; longer incisive
      foramen; vomerine sheath usually incomplete instead of always
      complete.

      _Specimens examined._--Total number, 10 (MN) from the type
      locality.


=Proechimys semispinosus amphichoricus= subspecies nova

      _Type locality._--Mount Duida, Esmeralda, _Amazonas_, Venezuela;
      altitude 325 m. _Type_: American Museum of Natural History, no.
      77020, adult male; collected 16 October 1920 by Olalla Bros.

      _Range._--Headwaters of Negro and Orinoco rivers, along boundary
      of Brazil and Venezuela.

      _Diagnosis._--Color dark, blackish on middorsal area; subapical
      zone of setiforms on back Buckthorn Brown, but many with distal
      parts black; skull broad across zygomata; nasals long;
      prepalatilar area of skull long; incisive foramen long and narrow;
      vomerine sheath complete; upper molars usually with four
      counterfolds but P4 usually with only three.

      _Pelage._--_Aristiforms on middorsal region_: Grayish basally,
      gradually blackening toward tip; total length, 18 to 20 mm;
      maximum width, 0.8 to 1.0 mm. _Setiforms on middorsal region_:
      Gray basally, gradually blackening toward tip but interrupted by a
      light (16 i), Buckthorn Brown, subapical zone 2 mm long; total
      length, 18 to 22 mm; maximum width, 0.03 mm. Most of them,
      however, whitish basally, gradually blackening toward tip without
      any distinctively-colored, subapical zone; total length, 24 to 26
      mm; maximum width, 0.5 mm. _Setiforms on outer thighs_: Whitish
      basally, gradually blackening toward tip but interrupted by an
      Ochraceous-Buff, subapical zone 3.5 mm long; black tip short; total
      length, 17 to 19 mm; maximum width, 0.05 mm.

_Skull._--Large and slender; rostrum elongate; nasals bluntly pointed
posteriorly; supraorbital ridges thick (but not expanded) and extending
across parietals but almost obsolete in middle part of parietals;
infraorbital foramen with weakly-developed groove for transmission of
nerve; postorbital process of zygoma involving mostly squamosal;
incisive foramen 5.5 x 2.8 mm wide in anterior third, with margins
constricted posteriorly and extending as ridges approximately 2 mm
beyond posterior margin of incisive foramen; posterior margin of
incisive foramen approximately 2.5 mm anterior to premolars; vomerine
sheath complete with maxillary part weak and premaxillary part extending
posteriorly beyond middle of incisive foramen; mesopterygoid fossa
extending forward as far as middle of M3; bullae well inflated and
elongated.

_Teeth._--P4 with four counterfolds in one of five specimens and with
three in remainder; M1 with four counterfolds in three of five specimens
and with three in remainder; M2 with three counterfolds in one specimen
and with four in all four remaining specimens; M3 always with four
counterfolds. Lower premolars with four counterfolds and lower molars
with only three.

_Comparisons._--The subspecies is easily distinguishable from _P. s.
angularis_ by: larger number of black setiforms on back, forming an
almost black longitudinal band; more elongate skull; larger and longer
bulla; longer incisive foramen which is more constricted posteriorly.

      _Specimens examined._--Total number, 6 (AMNH), as follows:
      Venezuela, territ. _Amazonas_, Esmeralda, Mt. Duida, altitude 325
      m., 4; Venezuela, territ. _Amazonas_, Rio Cassiquiare, Quemapuré,
      1; Brazil, Amazonas, _São Gabriel_, Rio Uaupés or Caiari, Tatú, 1.


=Proechimys semispinosus kermiti= Allen

      _Proechimys kermiti_ Allen, 30 December 1915, Bull. Amer. Mus. Nat.
      Hist., 34(22):629 (orig. descr.); Allen, 1916, Bull. Amer. Mus.
      Nat. Hist., 35(30):569; Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _Type locality._--Lower Rio Solimões (up the Solimões 50 to 60
      miles on the north bank of the river), _Manacaparú_, Amazonas,
      Brazil. _Type_: American Museum of Natural History, no. 37124,
      adult female; collected 20 April, 1914, by Leo E. Miller (Roosevelt
      Brazilian Expedition).

      _Range._--Known only from type locality.

      _Diagnosis._--Upper parts Tawny, with darker longitudinal band on
      back, gradually becoming Ochraceous-Buff on sides; zygomata widely
      spread; nasals long; incisive foramen long; vomerine sheath
      incomplete; only M3 with four counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Grayish basally,
      gradually blackening toward tip; total length, 18 to 20 mm;
      maximum width, 0.8 mm. _Setiforms on middorsal region_: Grayish
      basally, gradually blackening toward tip but interrupted by Tawny,
      subapical zone 2 mm long; total length, 18 to 20 mm; maximum
      width, 0.06 mm; some blackened toward tip without subapical zone.
      _Setiforms on outer thighs_: Whitish basally, gradually blackening
      toward tip but interrupted by Ochraceous-Buff, subapical zone
      2.5 mm long; total length, 18 to 20 mm; maximum width, 0.05 mm.

      _Skull._--Large, elongate, and strongly built; rostrum not
      conspicuously elongated; nasals bluntly pointed posteriorly;
      supraorbital ridges wide and extending posteriorly across parietals
      almost to level of interparietal; infraorbital foramen with
      moderate development of groove for transmission of nerve; zygomatic
      arches slender; postorbital process of zygoma involving mostly
      squamosal; incisive foramen 6.5 mm long and 2.7 mm wide, wider in
      anterior third and gradually constricted posteriorly, with margins
      extended toward palate as ridges; vomerine sheath incomplete,
      maxillary part threadlike; mesopterygoid fossa extending forward as
      far as anterior third of m3; bullae large and well inflated.

      _Teeth._--P4 with three counterfolds; M3 with four counterfolds;
      M1 and M2 with three counterfolds. Lower premolars with four
      counterfolds; lower molars with three counterfolds.

      _Comparisons._--From _P. s. amphichoricus_, _kermiti_ differs in:
      upper parts Tawny instead of Buckthorn Brown; incisive foramen
      longer and wider; vomerine sheath incomplete; only M3 instead of
      usually all molars, with four counterfolds. From _P. s.
      liminalis_, _kermiti_ differs in: upper parts Tawny instead of
      Ochraceous-Tawny; aristiforms narrower; M3 only, instead of
      usually M2 and M3, with four counterfolds.

      _Specimens examined._--Only the type.


=Proechimys longicaudatus= (Rengger)

      _General characters._--Size medium to large; tail short;
      aristiforms long and narrow; general color on upper parts
      Ochraceous-Buff to Ochraceous-Orange, finely and uniformly lined
      with blackish and not forming evident dark band on back; feet
      dorsally white or gray; underparts of body and inner sides of legs
      white; skull elongate and slender with moderate ridges; incisive
      foramen of medium size; vomerine sheath complete or incomplete;
      bullae large and elongate; upper molariform teeth with three
      counterfolds; lower molariform teeth with three counterfolds but
      commonly one or two molars have only two although premolar may have
      four.

_Remarks._--The identity of "_Echimys longicaudatus_ Rengger" can be
ascertained only after samples have been collected in the area indicated
by Rengger: "unter dem ein und zwansigsten Breitengrade" in Paraguay. Of
the samples available to me, those from Urucum, in western Brazil, are
geographically nearest the type locality. North of Urucum, both in
Brazil and Bolivia, two species of _Proechimys_ live together and one of
them is the same species as that at Urucum. Of the two species found to
the northward in Brazil and Bolivia, the one that ranges farther south
probably will occur at the locality indicated by Rengger. Provisionally,
therefore, the name _longicaudatus_ is allocated to the Urucum sample
(see Osgood, 1944:198). In fact, the lack of a type specimen and the
general nature of Rengger's description make "_Echimys longicaudatus_" a
_nomen vanum_. If two species are found living together in the region of
northern Paraguay indicated by Rengger it probably will be impossible to
be sure to which one his vague description applies.

The form from Urucum, to which the name _Proechimys longicaudatus_ is
here applied, is undoubtedly closely related to _Proechimys leucomystax_
Ribeiro, from Utiarití, on the Rio Papagaio and also to _P. roberti_ and
_P. boimensis_, all from Brazil. _P. longicaudatus_ is used as the name
of the species because it is the oldest of the four names.

[Illustration: FIGS. 45, 48. _Proechimys longicaudatus boimensis_, male,
MCZ no. 30881, Boim. × 1.]

[Illustration: FIGS. 46, 49. _Proechimys longicaudatus longicaudatus_,
male, AMNH no. 37085, Urucum. × 1.]

[Illustration: FIGS. 47, 50. _Proechimys longicaudatus leucomystax_,
male, AMNH no. 37509, Tapirapoã. × 1.]

[Illustration: FIGS. 51, 52. _Proechimys longicaudatus roberti_, male,
MN no. 6233, Pouso Alto, Goiaz. × 1.]

[Illustration: FIGS. 53, 54. _Proechimys longicaudatus boimensis_, male,
MCZ no. 30881, Boim. × 1.]

[Illustration: FIGS. 55, 56. _Proechimys longicaudatus longicaudatus_,
male, AMNH no. 37085, Urucum. × 1.]

[Illustration: FIGS. 57, 58. _Proechimys longicaudatus leucomystax_,
male, AMNH no. 37509, Tapirapoã. × 1.]

[Illustration: FIGS. 59, 60. _Proechimys longicaudatus roberti_, male,
MN no. 6233, Pouso Alto, Goiaz. × 1.]


=Proechimys longicaudatus brevicauda= (Günther)

      _Echimys brevicauda_ Günther, 1 April 1877, Proc. Zool. Soc. London
      for 1876, (49):748, fig. 9.

      _Proechimys brevicauda_ Ihering, 1904, Rev. Mus. Paulista, S.
      Paulo, 6:422; Osgood, 1914, Zool. Ser. Field Mus. Nat. Hist.,
      10(12):168; Thomas, 1924, Ann. Mag. Nat. Hist., 13 (ser. 9):534;
      Thomas, 1927, Ann. Mag. Nat. Hist., 19 (ser. 9):553; Thomas, 1927,
      Ann. Mag. Nat. Hist., 20 (ser. 9):604; Thomas, 1928, Ann. Mag.
      Nat. Hist., 2 (ser. 10):262; Thomas, 1928, Ann. Mag. Nat. Hist., 2
      (ser. 10):292; Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68
      (5):399; Osgood, 1944, Zool. Ser. Field Mus. Nat. Hist., 29
      (13):201.

      _Proechimys cayennensis brevicauda_ Ellerman, 1940, The families
      and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:120.

      _Type locality._--Chamicuros, Rio Huallaga, Peru. _Type_: British
      Museum (Nat. Hist.), no. 69.3.31.7,[F]; _Lectoparatype_: British
      Museum (Nat. Hist.), no. 66.1.29.8, from Upper Amazons (E.
      Barttet), selected by Thomas (1900:301).

      _Range._--Region of the headwaters and upper courses of the Juruá
      and Ucaiali rivers, eastern Peru and northwestern Brazil.

      _Diagnosis._--Upper parts Tawny and blackish without marked
      longitudinal band on back; underparts buffy or white; aristiforms
      narrow; skull slender; incisive foramen wide; vomerine sheath
      complete; molariform teeth with three counterfolds, except p4 with
      four and m3 with only two.

      _Pelage._--_Aristiforms on middorsal region_: Blackish basally,
      gradually blackening toward tip which is extended as a long
      filament; total length, 18 to 20 mm; maximum width, 0.65 mm.
      _Setiforms on middorsal region_: Gray basally, gradually
      blackening toward tip but interrupted by Tawny, subapical zone 1.2
      mm long; total length, 19 to 21 mm; maximum width, 0.1 mm.
      _Setiforms on outer thighs_: Whitish basally, gradually blackening
      toward tip but interrupted by Ochraceous-Tawny, subapical zone 3
      mm long.

      _Skull._--Slender but not elongated; nasals tapering posteriorly;
      interparietals wide; supraorbital ridges not much extended and
      faintly shown across parietals; jugals dorso-ventrally "wide" (3.5
      mm); postorbital process of zygoma weakly developed; incisive
      foramen 5.5 x 3 mm, oval, with posterior borders raised to form
      ridges which extend toward premolars; vomerine sheath complete,
      with maxillary part laterally compressed and extended toward
      palate as ridge; mesopterygoid fossa extending forward as far as
      third molars; bullae large and well inflated.

      _Teeth._--Molariform teeth with three counterfolds, except p4
      which has four and m3 which has only two counterfolds.

      _Comparisons._--From _P. l. longicaudatus_, _brevicauda_ differs
      in: upper parts Tawny instead of Ochraceous-Buff; lower premolar
      with four instead of three counterfolds; m3 only, instead of both
      m1 and m3, with two counterfolds. From _P. l. boimensis_,
      _brevicauda_ differs in: upper parts Tawny instead of
      Ochraceous-Orange; aristiforms wider; m3 with two instead of three
      counterfolds.

      _Specimens examined._--Total number, 3 (DZ), from Brazil, Amazonas,
      _João Pessoa_, Rio Juruá.


=Proechimys longicaudatus boimensis= J. A. Allen

      _Proechimys boimensis_ Allen, 24 July, 1916, Bull. Amer. Mus. Nat.
      Hist., 35(27):523; Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _Proechimys cayennensis_ Osgood, 1944, Zool. Ser. Field Mus. Nat.
      Hist., 29(13):199.

      _Type locality._--Boim, Rio Tapajoz, Santarem, Pará, Brazil.
      _Type_: American Museum of Natural History, no. 37486, adult male;
      "October 10, 1911 (ex Museu Goeldi)."

      _Range._--Along lower course of Tapajoz River.

      _Diagnosis._--Upper parts Ochraceous-Orange; incisive foramen
      posteriorly constricted; mesopterygoid fossa sharply pointed
      anteriorly; p4 with four counterfolds, remaining molariform teeth
      with three counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip which is extended as a long
      filament; total length, 16 to 18 mm; maximum width, 0.5 mm.
      _Setiforms on middorsal region_: Gray basally, gradually
      blackening toward tip, but interrupted by short (1.5 mm),
      Ochraceous-Orange, subapical zone; total length 18 to 20 mm;
      maximum width 0.09 mm. _Setiforms on outer thighs_: White basally,
      gradually blackening toward tip but interrupted by
      Ochraceous-Orange, or Ochraceous-Buff, subapical zone 3.5 mm long;
      total length 15 to 17 mm; maximum width, 0.06 mm.

      _Skull._--Elongate and slender; rostrum slender and long; nasals
      evenly pointed posteriorly; supraorbital ridges weak and barely
      reaching anteriormost part of parietals; zygomatic arches slender;
      infraorbital foramen with groove for nerve-transmission obsolete;
      postorbital process of zygoma weak and involving mostly squamosal;
      incisive foramen 5 mm long and 2.5 to 3 mm wide, oval, with
      margins not much extended caudad as ridges; posterior margin of
      incisive foramen approximately 2 mm anterior to premolars;
      vomerine sheath complete with maxillary part slender;
      mesopterygoid fossa sharply pointed anteriorly and extending
      forward as far as anterior part of third molar; bullae of medium
      size, smooth and more or less triangular in contour.

      _Teeth._--Crown length of upper molariform teeth 7 to 7.5 mm; all
      upper molariform teeth with three counterfolds; lower premolar
      with four counterfolds; lower molars with three counterfolds each.

      _Comparisons._--From three of the other four subspecies found in
      Brazil, _boimensis_ differs in having four, instead of three,
      counterfolds in the lower premolars. Differences from _P. l.
      brevicauda_ are indicated in the account of that subspecies.

_Remarks._--The material available from Boim, Tapajoz, is rather poor
and of no great significance. The Museu Nacional has one specimen from
Boim which agrees with the type in the American Museum of Natural
History. The Museum of Comparative Zoology at Harvard College, however,
has one specimen in its collection (MCZ no. 30888 [M]), adult, also from
Boim, in which the color pattern is different although agreement with
the type specimen is shown in cranial characters and width and length of
hairs. This specimen is much darker than the other specimens (of
orange-tint) assigned to this subspecies. However, in other samples of
this species, similarly dark animals have been noted. It seems that the
orange tint is gained only in old age. Another specimen (MCZ no. 30878
[F]) agrees in all respects with the type of the subspecies but the
locality recorded on the label is Cametá, on the Tocantins River.
Possibly the subspecies has a range so wide as to include Cametá but I
suspect that the data on the label is incorrect as to locality. The
collector marked [M] on the label although the specimen is a [F]. The
mistake might have occurred through labeling of specimens at a time
later than that at which they were collected. The collector was in both
localities on more than one occasion.

      _Specimens examined._--Total number, 5, from Brazil, Pará, as
      follows: _Santarem_, Rio Tapajoz, Boim, 3 (AMNH type, MCZ 1, MN 1);
      _Porto de Moz_, Tauarí, 1 (MCZ); _Cametá_ (?) 1 (MCZ).


=Proechimys longicaudatus longicaudatus= (Rengger)

      _Echimys longicaudatus_ Rengger, 1830, Naturgeschichte der
      Saeugethiere von Paraguay, p. 236.

      _Loncheres myosuros_ Lichtenstein, 1832, Darstellung neuer oder
      wenig bekannter Säugethiere, pl. 36 and text.

      _Echimys myosuros Is._ Geoffroy Saint-Hilaire, 1840, Mag. Zool.,
      Ann. 2 (ser. 2):15, 17; Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):261.

      _Echimys cayennensis_ Pictet, 1841, Mém. Soc. Phys. Hist. Nat.,
      Genéve, 9:145; Waterhouse, 1848, Nat. Hist. Mammalia, 2:334.

      _Proechimys longicaudatus_ Thomas, 1901, Ann. Mag. Nat. Hist., 8
      (ser. 7):532; Thomas, 1904, Proc. Zool. Soc. London, p. 240;
      Allen, 1916, Bull. Amer. Mus. Nat. Hist., 35(30):569; Tate, 1935,
      Bull. Amer. Mus. Nat. Hist., 68(5):400.

      _Proechimys cayennensis longicaudatus_ Ellerman, 1940, The
      families and genera of living rodents, Brit. Mus. (Nat. Hist.),
      1:121; Osgood, 1944, Zool. Ser. Field Mus. Nat. Hist, 29(13):198.

      _Type locality._--Northern Paraguay ("unter dem ein und zwansigsten
      Breitengrade"). _Type_: Apparently no type specimen was
      preserved.

      _Range._--Western Mato Grosso, Brazil, and northern Paraguay.

      _Diagnosis._--Upper parts almost uniformly Ochraceous-Buff;
      incisive foramen widest posteriorly; vomerine sheath complete; p4
      and m2 with three counterfolds; m1 and m3 usually with two
      counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Dark gray, gradually
      blackening toward tip that has long filament; total length 20 to
      22 mm; maximum width 0.6 mm. _Setiforms on middorsal region_:
      Whitish basally, gradually blackening toward tip but interrupted
      by Ochraceous-Buff, subapical zone; blackish tip extended (3.5 mm)
      and thin; total length 19 to 20 mm; maximum width 0.06 mm.
      _Setiforms on outer thighs_: Whitish basally, progressively
      grayish or blackish toward tip but interrupted by Light
      Ochraceous-Buff or Ochraceous-Buff, subapical zone; total length
      18 to 20 mm; maximum width 0.06 mm.

      _Skull._--Slender; supraorbital ridge notably raised; bullae
      large, elongate, smooth and inflated; jugals narrow; postorbital
      process of zygoma of medium size and constructed entirely of
      jugal; incisive foramen wide and large (5.5 x 3 mm), being
      wider posteriorly than anteriorly and with posterior margins
      raised; vomerine sheath complete, maxillary part slender
      and laterally flattened; mesopterygoid fossa extending forward as
      far as centers, or anterior margins, of third molars; posterior
      palatine foramina on plane with posterior faces, or centers, of
      second molars.

      _Teeth._--Upper molariform teeth always with three counterfolds.
      Lower molariform teeth: p4 and m2 always with three counterfolds,
      sometimes the two anterior ones coalesced in m2; m1 with three
      counterfolds in one specimen (33 per cent); m3 with only two
      counterfolds in all specimens.

      _Comparisons._--Differences from _P. l. leucomystax_ and _P. l.
      roberti_ are given in the accounts of those subspecies.

      _Specimens examined._--Total number, 3 (2 AMNH, 1 CNHM), from
      Brazil, Mato Grosso, _Corumbá_, Urucum.


=Proechimys longicaudatus leucomystax= Ribeiro

      _Proechimys leucomystax_ Ribeiro, May, 1914, Commissão de linhas
      telegraphicas estrategicas de Matto Grosso ao Amazonas, Annexo no.
      5. Hit. Nat., Zool., Mammiferos, p. 42, pl. 24 (orig. descr.);
      Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400; Ellerman, 1940,
      The families and genera of living rodents, Brit. Mus. (Nat. Hist.),
      1:119.

      _Type locality._--Utiarití, Rio Papagaio, Diamantion, Mato Grosso,
      Brazil. _Type_: Museu Nacional, no. 2212, adult, skull only,
      collected on 5 May 1909, by Prof. A. Miaranda Ribeiro, is here
      designated _lectotype_. See remarks.

      _Range._--Serra dos Parecís, Mato Grosso, Brazil.

      _Diagnosis._--Ochraceous-Buff, richly lined with blackish, on
      upper parts; some setiforms completely blackened distally;
      incisive foramen regularly ovoid; vomerine sheath incomplete;
      upper molariform teeth and lower premolar with three counterfolds;
      m2 with three counterfolds but m1 and m3 usually with two
      counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Grayish basally,
      gradually blackening toward tip which is extended as a long
      filament; total length 21 to 22 mm; maximum width 0.65 mm.
      _Setiforms on middorsal region_: Whitish basally, gradually
      blackening toward tip but interrupted by Ochraceous-Buff,
      subapical zone; some setiforms grayish basally and gradually
      blackening toward distal portion without any colored, subapical
      zone; total length 20 to 22 mm, maximum width 0.06 mm. _Setiforms
      on outer thigh_: White basally, gradually becoming gray toward tip
      but interrupted by Light Ochraceous-Buff, subapical zone; some
      setiforms gray basally and blackening toward tip, but interrupted
      by Ochraceous-Buff, subapical zone; total length 15 to 18 mm;
      maximum width 0.08 mm.

      _Skull._--Slender; supraorbital ridges conspicuous; bullae large,
      smooth and inflated, with slight, transverse groove; jugals
      narrow; postorbital processes of zygomata small and involving only
      squamosal; incisive foramen of medium size but narrow (5 x 2.5
      mm), regularly oval and with margins uplifted posteriorly;
      vomerine sheath incomplete but maxillary part projecting forward
      and sometimes almost reaching premaxillary part; mesopterygoid
      fossa reaching forward as far as centers of third molars;
      posterior palatine foramina at plane of posterior faces of second
      molars or slightly anterior thereto.

      _Teeth._--Upper molariform teeth with three counterfolds. Lower
      molariform teeth: p4 and m2 always with 3 counterfolds; m1 and m3
      with 2 counterfolds.

      _Comparisons._--From _P. l. longicaudatus_, _leucomystax_ differs
      in: upper parts richly lined, instead of scarcely lined, with
      blackish; incisive foramen narrower, and regularly oval instead of
      widest anteriorly.

      _Remarks._--_Proechimys leucomystax_ was described mainly on the
      basis of the Utiarití specimen, here designated lectotype of the
      species. The specimen from the Juina River is younger, as stated
      by Ribeiro in his description. Ribeiro mentions the skin of the
      specimen from Utiarití as "em muito mao estado" and I presume it
      was discarded as it has not been found in the collection of the
      Museu Nacional, Brazil.

      _Specimens examined._--Total number, 6, from Brazil, Mato Grosso:
      Cáceres, Salto Sepotube, 2 (MN); Cáceres, Tapirapoã, Rio Sepotuba,
      2 (AMNH); _Diamantino_, Utiarití, Rio Papagaio, 1 skull (MN);
      _Diamantino_, Rio Juina, 1 (MN).


=Proechimys longicaudatus roberti= Thomas

      _Proechimys roberti_ Thomas, December, 1901, Ann. Mag. Nat. Hist.,
      8 (ser. 7):531 (orig. descr.); Thomas, 1904, Ann. Mag. Nat. Hist.,
      14 (ser. 7):195; Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser.
      9):140; Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400.

      _Proechimys cayennensis roberti_ Ellerman, 1940, The families and
      genera of living rodents, Brit. Mus. (Nat. Hist.), 1:121.

      _Type locality._--Rio Jordão, _Araguarí_, Minas Gerais, Brazil; 960
      meters alt. _Type_: British Museum (Nat. Hist.), no. 1.11.3.62, old
      male, collected 8 August, 1902, by A. Robert; original number, 705.

      _Range._--Western Minas Gerais and southern Goiaz.

      _Diagnosis._--Color almost uniformly Ochraceous-Orange on upper
      parts; setiforms long and narrow; incisive foramen long and wide;
      vomerine sheath usually complete; upper molariform teeth and lower
      premolar with three counterfolds; m3 with two, and m1 and m2 with
      two or three, counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually blackening toward tip; total length, 21 to 23 mm;
      maximum width, 0.6 mm. _Setiforms on middorsal region_: Whitish on
      basal half, gradually blackening toward tip but interrupted by an
      Ochraceous-Orange, subapical zone 6 to 7 mm long; total length 25
      to 30 mm; maximum width, 0.05 mm. _Setiforms on outer thighs_:
      Whitish on basal half, gradually becoming gray and then blackish
      toward tip but interrupted by wide, Ochraceous-Buff, subapical
      zone, the tip being brownish or blackish; total length, 22 to 23
      mm; maximum width, 0.04 mm.

      _Skull._--Slender; supraorbital ridges bent outward and making
      sharp angle at point of frontosquamosal suture, then continuing
      backward parallel to each other and extending across parietals;
      squamosal taking small part in supraorbital ridges; bullae large
      (11 x 8 mm), inflated, with shallow depressions; incisive foramen
      not especially long but wide (5 x 3 to 3.5 mm), widest in anterior
      third and constricted posteriorly; vomerine sheath usually
      complete, with maxillary part reduced to slender threadlike
      process or, less commonly, missing; mesopterygoid fossa extending
      forward as far as centers of third molars; zygomatic arches strong
      with jugals of medium dorsoventral width (approximately 3.5 mm);
      postorbital process of zygoma weakly developed and involving only
      squamosal; posterior palatine foramina on plane of posterior
      margins of first molars or slightly anterior thereto.

[Illustration: FIG. 61. Map showing the geographic ranges of the
subspecies of three species of the subgenus _Proechimys_ in Brazil.]

      _Teeth._--Upper molariform teeth usually with three counterfolds
      (92.5 per cent of 42 specimens); M2 with four counterfolds in 5 per
      cent of specimens; M3 with two counterfolds in 2.5 per cent of
      specimens. Lower molariform teeth: p4 usually with three
      counterfolds (97.5 per cent of 39 specimens); rarely with four (2.5
      per cent); m1 with three counterfolds in 58 per cent and two
      counterfolds in 42 per cent of specimens; m2 with three
      counterfolds in 61 per cent and two counterfolds in 39 per cent of
      specimens; m3 always with only two counterfolds.

      _Comparisons._--From _P. l. boimensis_, _roberti_ differs in: wider
      incisive foramen; lower premolar with three, and one or two lower
      molars with only two, counterfolds, instead of lower premolar with
      four and all lower molars with three counterfolds. From _P.
      longicaudatus_, _roberti_ differs in: upper parts Ochraceous-Orange
      instead of Ochraceous-Buff; incisive foramen wider in posterior
      third than in anterior third.

_Remarks._--This subspecies seems to be adapted to forests of
post-climactic conditions which is probably typical of most valleys and
margins of the rivers in southern Goiaz and western Minas Gerais. It was
found in Goiaz usually in riparian forests with climactic associations
or in some advanced stage of the sere. The animals also make incursions
into nearby open areas or crops of corn.

      _Specimens examined._--Total number, 52, from Brazil, as follows:
      Minas Gerais, _Araguarí_, Rio Jordão (effluent of Parnaiba), 960
      meters alt., 2 (1 CNHM, 1 DZ); Goiaz, _Anapolis_, 1010 meters alt.,
      38 (MN); Goiaz, _Pouso Alto_, 768 meters alt., 11 (MN); Goiaz, Tio
      São Miguel, 2 (MN).


=Proechimys guyannensis= (E. Geoffroy)

      _Mus guyannensis_ E. Geoffroy Saint-Hilaire, 1803, Catalogue des
      mammifères du Museum d'Histoire Naturelle, Paris, p. 194.

      _Echimys cayennensis_ Desmarest, 1817, Nouv. Dict. Hist. Nat.,
      Paris, nouv. ed., 10:59.

      _Proechimys cayennensis_ Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):261, 264; Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):399; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:120.

      _General characters._--Size medium to large; tail usually short;
      aristiforms narrow to wide; general color of setiforms on back
      ranging from Tawny to Ochraceous-Buff and becoming gradually
      lighter on sides; no conspicuous dark longitudinal band on back;
      upper parts of hands and feet white to light brown; underparts
      white, including inner sides of legs; skull elongate and not
      conspicuously ridged; vomerine sheath complete or incomplete; upper
      premolar with three counterfolds and molars with two or three;
      lower premolar with three or four counterfolds, and lower molars
      with two or three.


=Proechimys guyannensis villicauda= subspecies nova

      _Type locality._--Tapirapoã, Rio Sepotuba, _Cáceres_, Mato Grosso,
      Brazil. _Type_: Museu Nacional, no. 1932, adult male (color faded);
      collected on 2 February, 1909, by Prof. A. Miranda Ribeiro;
      original number, 788 A.

      _Range._--Serra dos Parecís, headwaters of Paraguai and Tapajoz
      rivers.

      _Diagnosis._--Aristiforms wide and stiff; general color on upper
      parts Ochraceous-Orange; incisive foramen long; vomerine sheath
      incomplete or complete; lower premolar with four counterfolds,
      remaining molariform teeth with three counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually becoming gray toward tip, with distal fourth blackish
      and ending as a long filament; total length, 22 to 23 mm; maximum
      width, 1 mm. _Setiforms on middorsal region_: Whitish on basal
      half, gradually blackening toward tip but interrupted by
      Ochraceous-Orange, subapical zone 5 mm long; total length, 26 to
      30 mm; width, 0.04 to 0.12 mm. _Setiforms on outer thighs_: Whitish
      on basal half, gradually blackening toward tip but interrupted by
      Ochraceous-Buff to Ochraceous-Orange subapical zone; total length
      20 to 23 mm; width, 0.03 to 0.18 mm.

      _Skull._--Strong; supraorbital ridges raised and extending across
      anterior fourth of parietals; nasals elongate; bullae rounded,
      inflated, with shallow grooves; postorbital process of zygoma
      weakly developed and constructed entirely of jugal; incisive
      foramen elongate and narrow (5.5 x 2.5 mm), posteriorly constricted
      with posterior margins elevated above surface of bones; vomerine
      sheath incomplete or complete but, when complete, with maxillary
      part filiform and delicate; mesopterygoid fossa extending forward
      as far as middle, or even anterior, parts of third molars;
      posterior palatine foramina on plane of centers, or even anterior
      faces, of second molars.

      _Teeth._--Upper molariform teeth with three counterfolds. Lower
      molariform teeth: premolar with four counterfolds, molars with
      three counterfolds, sometimes with two folds coalesced in center
      of tooth.

      _Comparison._--From _P. g. ribeiroi_, and _P. g. bolivianus_,
      _villicauda_ differs in wider aristiforms. From _P. g. ribeiroi_,
      _villicauda_ further differs in: larger and wider incisive
      foramen; vomerine sheath incomplete or complete instead of always
      complete and thick. From _P. g. bolivianus_, _villicauda_ differs
      in: lower premolars always, instead of rarely, with four
      counterfolds, and m3 always with three counterfolds instead of
      usually with only two counterfolds.

      _Specimens examined._--Total number, 4, from Brazil, Mato Grosso,
      as follows: _Cáceres_, Tapirapoã, 3 (MN); _Diamantino_, Rio
      Papagaio, Utiarití, 1 (AMNH).

[Illustration: FIG. 62.
_Proechimys guyannensis villicauda_, male, MN no. 1932, Tapirapoã.
Type. × 1.]

[Illustration: FIG. 63. _Proechimys guyannensis ribeiroi_, male, MN no.
1935, Rio Doze de Outubro. Type. × 1.]

[Illustration: FIG. 64. _Proechimys guyannensis hyleae_, male, MCZ no.
30887, Tauarí. Type. × 1.]

[Illustration: FIG. 65. _Proechimys guyannensis nesiotes_, male, CNHM
no. 19496, Ilha de Manapirí. Type. × 1.]

[Illustration: FIG. 66. _Proechimys guyannensis leioprimna_, female,
CNHM no. 19503, Cametá. Type. × 1.]

[Illustration: FIG. 67. _Proechimys guyannensis oris_, male, CNHM no.
19495, Providencia. × 1.]

[Illustration: FIG. 68. _Proechimys guyannensis arescens_, male, CNHM
no. 26440, Fazenda Inhuma. Paratype. × 1.]

[Illustration: FIG. 69. _Proechimys guyannensis riparum_, female, AMNH
no. 143018, Manaus. Type. × 1.]

[Illustration: FIG. 70. _Proechimys guyannensis arabupu_, male, AMNH no.
75816, Arabupu. Type. × 1.]

[Illustration: FIG. 71. _Proechimys guyannensis villicauda_, male, MN
no. 1932, Tapirapoã. Type. × 1.]

[Illustration: FIG. 72. _Proechimys guyannensis ribeiroi_, male, MN no.
1935, Rio Doze de Outubro. Type. × 1.]

[Illustration: FIG. 73. _Proechimys guyannensis hyleae_, male, MCZ no.
30887, Tauarí. Type. × 1.]

[Illustration: FIG. 74. _Proechimys guyannensis nesiotes_, male, CNHM
no. 19496, Ilha de Manapirí. Type. × 1.]

[Illustration: FIG. 75. _Proechimys guyannensis leioprimna_, female,
CNHM no. 19503, Cametá. Type. × 1.]

[Illustration: FIG. 76. _Proechimys guyannensis oris_, male, CNHM no.
19495, Providencia. × 1.]

[Illustration: FIG. 77. _Proechimys guyannensis arescens_, male, CNHM
no. 26440, Fazenda Inhuma. Paratype. × 1.]

[Illustration: FIG. 78. _Proechimys guyannensis riparum_, female, AMNH
no. 143018, Manaus. Type. × 1.]

[Illustration: FIG. 79. _Proechimys guyannensis arabupu_, male, AMNH no.
75816, Arabupu. Type. × 1.]

[Illustration: FIGS. 80, 81. _Proechimys guyannensis villicauda_, male,
MN no. 1932, Tapirapoã. Type. × 1.]

[Illustration: FIGS. 82, 83. _Proechimys guyannensis ribeiroi_, male, MN
no. 1935, Rio Doze de Outubro. Type. × 1.]

[Illustration: FIGS. 84, 85. _Proechimys guyannensis hyleae_, male, MCZ
no. 30887, Tauarí. Type. × 1.]

[Illustration: FIGS. 86, 87. _Proechimys guyannensis nesiotes_, male,
CNHM no. 19496, Ilha de Manapirí. Type. × 1.]

[Illustration: FIGS. 88, 89. _Proechimys guyannensis leioprimna_,
female, CNHM no. 19503. Type. × 1.]

[Illustration: FIGS. 90, 91. _Proechimys guyannensis oris_, male, CNHM
no. 19495, Providencia. × 1.]

[Illustration: FIGS. 92, 93. _Proechimys guyannensis arescens_, male,
CNHM no. 26440, Fazenda Inhuma. Paratype. × 1.]

[Illustration: FIGS. 94, 95. _Proechimys guyannensis riparum_, female,
AMNH no. 143018, Manaus. Type. × 1.]

[Illustration: FIGS. 96, 97. _Proechimys guyannensis arabupu_, male,
AMNH no. 75816, Arabupu. Type. × 1.]


=Proechimys guyannensis ribeiroi= subspecies nova

      _Type locality._--Rio 12 de Outubro, affluent of the Camararé,
      _Mato Grosso_, Mato Grosso, Brazil; about 190 kilometers west of
      Utiarití; altitude 414 meters. _Type_: Museu Nacional, no. 1935,
      adult male (colors faded); collected on 20 June, 1909, by Prof. A.
      Miranda Ribeiro; original number _G._

      _Range._--Known only from the type locality.

      _Diagnosis._--_Aristiforms wide and stiff_; incisive foramen small
      and narrow; vomerine sheath complete and thick; p4 with four
      counterfolds; remaining molariform teeth with three counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually blackening toward tip; total length, 19 to 22 mm;
      maximum width, 0.8 mm. _Setiforms on middorsal region_: Whitish on
      basal half, gradually blackening toward tip but interrupted by
      subapical zone probably of some tint of ochraceous; total length,
      22 to 24 mm; maximum width, 0.06 mm. _Setiforms on outer thighs_:
      Whitish basally, gradually blackening toward tip but interrupted
      by probably light ochraceous, subapical zone; total length 14 to
      16 mm; maximum width, 0.03 mm.

      _Skull._--Slender; supraorbital ridges low; bullae ovate with
      shallow grooves; postorbital process of zygoma almost obsolete and
      involving mostly jugal; incisive foramen short and narrow (4 × 2
      mm), constricted posteriorly and with posterior margins raised;
      vomerine sheath complete and thick; mesopterygoid fossa extending
      forward as far as posterior faces of second molars; posterior
      palatine foramina on plane with centers of second molars.

      _Teeth._--Upper molariform teeth with three counterfolds. Lower
      molariform teeth: p4 with four counterfolds; molars with three
      counterfolds which sometimes are fused.

      _Comparisons._--From _P. g. bolivianus_, _ribeiroi_ differs in:
      aristiforms wider; incisive foramen shorter and narrower; vomerine
      sheath complete and thick, instead of complete or incomplete and
      not thick; p4 always with four, instead of usually only three,
      counterfolds and lower molars always with three, instead of
      sometimes with only two, counterfolds in m3. Differences from _P.
      g. villicauda_ are given in the account of that subspecies.

_Remarks._--The name _ribeiroi_ is given in honor of the late Professor
Alipio Miranda Ribeiro, in recognition of his important work in
Brazilian vertebrate zoology.

      _Specimens examined._--Total number, 2 (MN), from Brazil, Mato
      Grosso, _Mato Grosso_, Rio 12 de Outubro; altitude, 414 meters.


=Proechimys guyannensis hyleae= subspecies nova

      _Type locality._--Tauarí, Rio Tapajoz, _Porto de Moz_, Pará,
      Brazil; approximately 87 kilometers south of Santarem. _Type_:
      Museum of Comparative Zoology at Harvard College, no. 30887, adult
      male; collected on 19 January, 1934, by A. M. Olalla; original
      number 7288.

      _Range._--Region of lower Tapajoz River and banks of Amazon up to
      the Jamundá River.

      _Diagnosis._--Aristiforms conspicuously wide and stiff; general
      color on upper parts Tawny; incisive foramen long and oval;
      vomerine sheath complete but with maxillary part slender or,
      sometimes, incomplete; p4 with four counterfolds, rarely three;
      remaining molariform teeth with three counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually becoming blackish toward tip; total length, 19 to 21 mm;
      maximum width, 1.1 mm. _Setiforms on middorsal region_: a. Gray
      basally, gradually blackening toward tip but interrupted by wide (5
      to 6 mm) Tawny, subapical zone; some are whitish basally and
      gradually become sooty brown toward tip except for same type of
      subapical zone (tip only slightly darker than subapical zone); b.
      With the same type described above and some completely blackish,
      with the base gray; total length 22 to 25 mm; maximum width, 0.1
      mm. _Setiforms on outer thighs_: Whitish basally, gradually
      becoming gray and then blackish toward tip but interrupted by long,
      Ochraceous-Tawny, subapical zone; tip, itself, blackish brown;
      sometimes this type appears with some lighter ones and sometimes
      with completely blackish setiforms; total length 16 to 18 mm;
      maximum width 0.3 mm.

      _Skull._--Medium in size and slender; cranium narrow and not
      increasing much in breadth posteriorly; rostrum stout, laterally
      thick, with masseteric crest well-developed; nasals pointed
      posteriorly; supraorbital ridges broad but barely extended across
      parietals; zygomatic arches strong; postorbital process of zygoma
      involving mostly squamosal; incisive foramen long and narrow (5.5
      to 6 × 2.5 mm), oval and extending posteriorly to point only 2 mm
      anterior to premolars; vomerine sheath complete with maxillary
      part usually slender; mesopterygoid fossa extending forward as far
      as centers of third molars; bulla of medium size, well inflated
      and with shallow grooves on surface.

      _Teeth._--Upper molariform teeth with three counterfolds. Lower
      premolar with four counterfolds or, sometimes (20 per cent of 15
      specimens), with only three; lower molars with three counterfolds.

      _Comparisons._--From _P. g. oris_ and _P. g. nesiotes_, _hyleae_
      differs in: wider aristiforms; general color on upper parts Tawny,
      instead of Ochraceous-Orange; vomerine sheath not always complete,
      instead of always complete. From _P. g. oris_, _hyleae_ differs
      in: p4 usually with four, instead of only three counterfolds and
      all molars with three, instead of only lower molars with three
      counterfolds. From _P. g. nesiotes_, _hyleae_ differs in: p4
      usually, instead of always, with four counterfolds; color on back
      Tawny instead of Ochraceous-Orange; aristiforms wider.

_Remarks._--This subspecies shows greater variability than any other in
this species. There are two types of coloration. The most common type of
coloration is dark, with Tawny, subapical zones in the setiforms of the
middorsal region and many completely black setiforms; in the other type
the subapical zone is still Tawny but there are no black setiforms. One
specimen from Obidos, on the north bank of the Amazon, completely agrees
in the characteristics of color and skull with the reddish type and
suggests either that there is an extension of the range of the
subspecies along the lower course of the Tapajoz or that there are two
subspecies, in which event the animals from Tauarí are intergrades
between _hyleae_ and an unnamed, tawny-colored subspecies occurring to
the southward.

Between 13 and 23 January, 1934, A. M. Olalla collected 10 adult
females, 6 of which contained embryos. Three of the females had 2
embryos each, two had 3 embryos each and one had only 1 embryo. At this
same time and place only ten per cent of specimens obtained were not
fully adult.

      _Specimens examined._--Total number, 21, from Brazil, Pará, as
      follows: _Porto de Moz_, Tauarí, right bank of Tapajoz,
      approximately 85 kilometers south of Santarem, 20 (19 MCZ, 1 CNHM);
      _Obidos_, Obidos, 1 (MCZ).


=Proechimys guyannensis nesiotes= subspecies nova

      _Type locality._--Ilha de Manapirí, Rio Tocantins, Pará,
      Brazil. _Type_: Chicago Natural History Museum, no. 19496, adult
      male; collected on 9 December, 1910, by Dr. Emilia Snethlage;
      original number, 12.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms wide and stiff; general color on upper
      parts Ochraceous-Orange; incisive foramen long, with parallel
      borders; vomerine sheath complete and thick; p4 with four
      counterfolds, remaining molariform teeth with three counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 18 to 19 mm;
      maximum width, 0.9 mm. _Setiforms on middorsal region_: Gray
      basally, gradually blackening toward tip but interrupted by
      Ochraceous-Orange, subapical zone 4 mm long; total length 16 to 19
      mm; maximum width, 0.06 mm. _Setiforms on outer thighs_: Whitish
      basally, gradually becoming gray and blackish toward tip but
      interrupted by Ochraceous-Buff, subapical zone 3 mm long; total
      length, 13 to 15 mm; maximum width, 0.03 mm.

      _Skull._--Of medium size; rostrum short; nasals pointed
      posteriorly; postorbital ridges extending caudad across anterior
      fifth of parietals; zygomatic arches strong; jugal with process in
      posterior part of masseteric fossa; postorbital process of zygoma
      involving mostly squamosal; incisive foramen elongate, narrow (5 x
      2.3 mm), and parallel sided; posterior margin of incisive foramen
      approximately 3 mm anterior to premolars; margins of foramen
      raised to form ridges; vomerine sheath complete, of almost uniform
      width and set deeply in foramen; mesopterygoid fossa extending
      forward as far as centers of third molars; bullae of medium size
      and inflated.

      _Teeth._--Upper molariform teeth with three counterfolds; p4 with
      four counterfolds; m1-3 with three counterfolds.

      _Comparison._--_From P. g. oris_, _nesiotes_ differs in:
      Aristiforms conspicuously wider; incisive foramen shorter and
      narrower, with borders parallel instead of posteriorly
      constricted; posterior margin of incisive foramen farther from
      premolars; p4 with four, instead of three, counterfolds; lower
      molars with three instead of two counterfolds. From _P. g.
      leioprimna_, _nesiotes_ differs in: Incisive foramen with parallel
      borders instead of oval; p4 with four instead of three
      counterfolds; m3 always with three instead of two counterfolds.

_Remarks._--Dr. E. Snethlage mentions the type as having been collected
at night in the forest.

      _Specimens examined._--Total number, 8 (MCZ, CNHM, MN), from
      Brazil, Pará, Tocantins River, Ilha de Manapirí.


=Proechimys guyannensis leioprimna= subspecies nova

      _Type locality._--Cametá, left bank of Tocantins River, near its
      mouth, Cametá, Pará, Brazil. _Type_: Chicago Natural History
      Museum, no. 19503, adult female; collected on 21 January, 1911, by
      Dr. Emilia Snethlage; original number, 35.

      _Range._--Known only from type locality but probably extending
      westward toward Xingú River.

      _Diagnosis._--Aristiforms wide and stiff; general color on upper
      parts Ochraceous-Orange, incisive foramen moderately long; oval;
      vomerine sheath complete; all molariform teeth with three
      counterfolds, except lower, third molar which has only two.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip which is extended as a short
      filament; total length, 19 to 21 mm; maximum width, 0.8 to 1 mm.
      _Setiforms on middorsal region_: Whitish basally, gradually
      blackening toward tip but interrupted by Ochraceous-Orange,
      subapical zone 2 to 3 mm long; total length, 17 to 20 mm; maximum
      width 0.1 mm. _Setiforms on outer thighs_: Whitish basally,
      becoming gradually gray and then blackish toward tip but
      interrupted by Ochraceous-Buff, subapical zone; blackish tip
      short; total length 13 to 15 mm; maximum width 0.06 mm.

      _Skull._--Of medium size; rostrum relatively short; nasals with
      posterior borders rounded; postorbital ridges extending across
      anterior fourth of parietals; zygomatic arches moderately strong;
      postorbital process of zygoma involving both jugal and squamosal;
      incisive foramen of medium length (4 to 5 mm) and narrow (about
      2.5 mm), oval and extending caudad to a plane approximately 2 mm
      anterior to premolars; vomerine sheath complete, with premaxillae
      forming approximately anterior 3/4 of sheath; maxillary part of
      sheath short but well-developed; mesopterygoid fossa extending
      forward as far as centers of third molars; bullae of medium size
      but well-inflated.

      _Teeth._--Upper molariform teeth with three counterfolds. Lower
      molariform teeth with three counterfolds, except third molar which
      has only two.

      _Comparison._--From _P. g. oris_, _leioprimna_ differs in:
      conspicuously wider aristiforms; shorter and narrower incisive
      foramen; lower molariform teeth with three counterfolds (except m3
      with only two), instead of lower molars with only two
      counterfolds. Differences from _P. g. nesiotes_ are given in the
      account of that subspecies.

_Remarks._--The paratype was collected in an "igarapé," depression
usually invaded by the river waters; the paratype, collected on 18
January, 1911, had two large embryos.

      _Specimens examined._--Total number, 4 (2 CNHM, 2 AMNH), from
      Brazil, Pará, Cametá.


=Proechimys guyannensis oris= Thomas

      _Proechimys oris_ Thomas, September, 1904, Ann. Mag. Nat. Hist., 14
      (ser. 7): 195; Thomas, 1905, Ann. Mag. Nat. Hist., 15 (ser. 7):587;
      Thomas, 1912, Ann. Mag. Nat. Hist., 9 (ser. 8):89; Tate, 1935,
      Bull. Amer. Mus. Nat. Hist., 68:400; Osgood, 1944, Zool. Ser. Field
      Mus. Nat. Hist., 29:199.

      _Proechimys cayennensis oris_ Ellerman, 1940, The families and
      genera of living rodents, Brit. Mus. (Nat. Hist.), 1:121.

      _Type locality._--Igarapé-assú, E. F. B., near Belem, Igarapé-assú,
      Pará, Brazil. _Type_: British Museum (Nat. Hist.), no. 4.7.4.78,
      old male; collected on 6 March, 1904, by Alphonse Robert; original
      number, 1818.

      _Range._--Probably most of the region on south bank of Amazon
      River, between Tocantins (west) and Gurupí River (south).

      _Diagnosis._--Aristiforms narrow but somewhat stiff; color on
      upper parts Ochraceous-Orange; incisive foramen long and wide,
      conspicuously constricted posteriorly; posterior margin of incisive
      foramen close to plane of premolars; vomerine sheath complete but
      maxillary part threadlike; upper molariform teeth and lower
      premolar with three counterfolds; lower molars with only two
      counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip, which is extended as a filament;
      total length, 16 to 17 mm; maximum width, 0.6 to 0.7 mm.
      _Setiforms on middorsal region_: Gray basally, gradually becoming
      blackish toward tip but interrupted by Ochraceous-Orange,
      subapical zone 2 to 4 mm long; total length, 18 to 20 mm; maximum
      width 0.06 mm. _Setiforms on outer thighs_: Whitish basally,
      gradually becoming blackish toward tip but interrupted by
      Ochraceous-Buff, subapical zone; total length, 15 to 16 mm;
      maximum width, 0.04 mm.

      _Skull._--Of medium size; supraorbital ridges well developed and
      extending across anterior fifth of parietals; zygomatic arches
      strong; jugal with masseteric fossa deep and with well-developed
      posterior process; postorbital zygomatic process involving mostly
      squamosal; incisive foramen long (6 to 7 mm), widest anteriorly
      (2.5 to 3.2 mm); but narrowing posteriorly to less than 1 mm and
      extending caudad almost to plane of premolars; vomerine sheath
      complete but maxillary part delicate and threadlike; mesopterygoid
      fossa extending forward as far as third molars or posterior parts
      of second molars; bullae large and inflated.

      _Teeth._--Each upper molariform tooth with three counterfolds. In
      lower jaw, premolar with three, and molars with only two,
      counterfolds.

      _Comparisons._--Differences from the subspecies with adjoining
      ranges are given in the accounts of those subspecies.

_Remarks._--Thomas (1912:89) extended the known range of the subspecies
to Faro, on the Jamundá River, on the left bank of the Amazon, and to
Boim, on the Tapajoz River, as well as to Benevides, E. F. Braganca,
near Belem. It seems to me that the specimens from Faro should be
referred provisionally to _Proechimys guyannensis hyleae_; the specimens
from Boim are "more brightly rufous" (Thomas, _loc. cit._) and could be
referred to Allen's _P. boimensis_, described in 1914, but _P.
guyannensis hyleae_ probably lives in the same place and only an
examination of the specimens, which I have not seen, would permit of
certainly allocating the specimens to their correct species. The
specimens from Benevides are more certainly _P. g. oris_.

E. Snethlage collected one specimen in a garden (Providencia, E. F. B.).
However, according to the personnel of the Brazilian Health Service, the
animals are strictly forest dwellers although they do make excursions
into more open places.

      _Specimens examined._--Total number, 3, from Brazil, Pará, as
      follows: Providencia, E. F. B., approximately 15 kilometers east
      from Belem, 1 (CNHM); Tanaquará, near Belem, 1 (MN); Rio Guamá,
      near Belem, 1 (AMNH).

      _Additional record._--Brazil, Pará, Benevides, E. F. B.,
      approximately 100 kilometers north-east of Belem (Thomas,
      1912:89).


=Proechimys guyannensis arescens= Osgood

      _Proechimys cayennensis arescens_ Osgood, 12 July 1944, Zool. Ser.
      Field Mus. Nat. Hist., 29(13): 198.

      _Type locality._--Fazenda Inhuma, below Santa Filomena, upper Rio
      Parnaiba, _Vitoria do Alto Parnaiba_, Maranhão, Brazil. _Type_:
      Chicago Natural History Museum, no. 26441, adult male; collected on
      5 August, 1925, by Heinrich E. Snethlage.

      _Range._--Region including the valleys of the Turí-assú and
      Parnaiba rivers, Maranhão, Brazil.

      _Diagnosis._--Aristiforms moderately wide and not conspicuously
      stiff; general color of upper parts near (15'a) Ochraceous-Orange;
      incisive foramen long and wide; vomerine sheath complete or
      incomplete; upper molariform teeth and lower premolar with three
      counterfolds; lower molars with only two.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually blackening toward tip; total length, 19 to 21 mm;
      maximum width, 0.7 mm. _Setiforms on middorsal region_: Whitish
      basally or on basal half, gradually becoming gray and then
      blackish toward tip, but interrupted by long (5 to 6 mm) subapical
      zone near (15'_a_) Ochraceous-Orange; total length, 15 to 16 mm;
      maximum width 0.05 mm. _Setiforms on outer thighs_: Whitish on
      basal half, gradually becoming gray and then blackish toward tip
      but interrupted by Ochraceous-Buff, subapical zone; tip sometimes
      not conspicuously darker than subapical zone; total length 18 to
      25 mm; maximum width, 0.03 mm.

      _Skull._--Medium in size, not elongated; nasals pointed
      posteriorly; supraorbital ridges strong and thick, extending
      caudad across anterior third of parietals; zygomatic arches
      strong; postorbital process of zygoma involving only squamosal;
      incisive foramen 5 by 2.7 mm, oval and extending caudad to plane
      approximately 2 mm anterior to premolars; posterior margins of
      incisive foramen not forming a ridge; vomerine sheath complete and
      with maxillary part slender and threadlike, or incomplete, in
      which event, maxillary part not extended enough to join
      premaxillary process; mesopterygoid fossa extending forward
      as far as centers of third molars; bulla large and more or less
      triangular in its peripheral outline.

      _Teeth._--Upper molariform teeth with three counterfolds each.
      Lower premolar with three counterfolds; lower molars with two
      counterfolds.

      _Comparisons._--From _P. g. oris_, _arescens_ differs in: Color of
      upper parts lighter and more uniform; incisive foramen oval
      instead of conspicuously constricted posteriorly; posterior margin
      of incisive foramen farther from premolars.

_Remarks._--One specimen from Turí-assú (MN) has been identified by O.
Thomas as "_P. oris_" (his own handwriting is on the label) and the
subspecies is really closely related to _oris_.

      _Specimens examined._--Total number, 3, from Brazil, Maranhão, as
      follows: _Vitoria do Alto Parnaiba_, Fazenda Inhuma (below Santa
      Filomena), 2 (CNHM); Alto da Alegria, Turí-assú, 1 (MN).


=Proechimys guyannensis riparum= subspecies nova

      _Type locality._--Manaus, _Manaus_, Amazonas, Brazil. _Type_:
      American Museum of Natural History, no. 143018, adult female;
      collected 6 March, 1943.

      _Range._--Known only from type locality but probably extending
      northward and eastward.

      _Diagnosis._--Aristiforms wide and stiff; upper parts
      Ochraceous-Tawny; incisive foramen short, wide, and oval; vomerine
      sheath incomplete; upper molariform teeth and lower premolar with
      three counterfolds; lower molars with only two counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally
      gradually blackening toward tip; total length, 18 to 20 mm;
      maximum width, 0.9 mm. _Setiforms on middorsal region_: Whitish
      basally, gradually blackening toward tip but interrupted by 2 mm
      long, Ochraceous-Tawny, subapical zone; total length 20 to 22 mm;
      maximum width, 0.04 mm. Some are whitish basally and gradually
      become black toward tip with no subapical zone. _Setiforms on
      outer thighs_: Whitish basally, gradually becoming gray and then
      blackish toward tip but interrupted by Ochraceous-Buff, subapical
      zone 3 to 4 mm long; tip not conspicuously dark; total length, 17
      to 19 mm; maximum width, 0.03 mm.

      _Skull._--Of medium size and slender; rostrum slender; nasals
      rounded posteriorly; supraorbital ridges well developed and barely
      extended onto anteriormost part of parietals; zygomatic arches
      slender; infraorbital foramen with well-developed groove for nerve
      transmission; postorbital process of zygoma almost obsolete and
      involving mostly squamosal; incisive foramen short and wide (4.5 ×
      3.3 mm), oval and with posterior margins raised to form ridges
      which extend toward premolars; posterior margin of incisive
      foramen approximately 2.5 mm anterior to premolars; vomerine
      sheath incomplete, with only short, premaxillary part;
      mesopterygoid fossa extending forward as far as anterior
      parts of third molars; bullae large and inflated, with more or
      less triangular outline.

      _Teeth._--Crown length of well worn P4-M3, 6.8 mm; upper
      molariform teeth with three counterfolds each. Lower premolar
      with three counterfolds; lower molars with two counterfolds.

[Illustration: FIG. 98. Map showing the geographic ranges of the
subspecies of _Proechimys guyannensis_ in Brazil.]

      _Comparisons._--From _P. g. oris_ and _P. g. hyleae_, _riparum_
      differs in: Shorter and wider incisive foramen; vomerine sheath
      incomplete, instead of sometimes incomplete. From _P. g. oris_,
      _riparum_ differs in: Upper parts Ochraceous-Tawny instead of
      Ochraceous-Orange; aristiforms conspicuously wider. From _P. g.
      hyleae_, _riparum_ differs in: Aristiforms narrower; upper parts
      Ochraceous-Tawny instead of Tawny; lower premolars with three,
      instead of four, counterfolds; lower molars with two, instead of
      three, counterfolds.

      _Specimens examined._--Type only.


=Proechimys guyannensis arabupu= subspecies nova

      _Type locality._--Arabupu, Mount Roraima, _Bõa Vista_, Territ. Rio
      Branco; about 1540 meters altitude. _Type_: American Museum of
      Natural History, no. 75816, adult male; collected by Dr. G. H. H.
      Tate on 30 December, 1927; original number, 4716.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms conspicuously wide and stiff; color on
      upper parts dark, near (15'_j_) Ochraceous-Tawny; incisive foramen
      widest in anterior third; vomerine sheath complete, sometimes
      incomplete; upper molariform teeth and lower premolar with three
      counterfolds; lower molars with two counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Whitish basally,
      gradually blackening toward tip; total length, 19 to 22 mm;
      maximum width, 1.1 mm. _Setiforms on middorsal region_: Gray
      basally, gradually blackening toward tip but interrupted by dark
      (15'j) Ochraceous-Tawny, subapical zone 3 mm long; some completely
      blackish on distal parts; total length, 20 to 23 mm; maximum
      width, 0.07. _Setiforms on outer thighs_: Whitish basally,
      gradually blackening toward tip but interrupted by Ochraceous-Buff
      or Light Ochraceous-Buff, subapical zone; total length, 20 to 23
      mm; maximum width, 0.07 mm.

      _Skull._--Size medium; nasals pointed posteriorly; supraorbital
      ridges prominent and slightly extended caudad onto anterior half
      of parietals; groove for transmission of nerve in infraorbital
      foramen weakly developed; zygomatic arches strong; postorbital
      process of zygoma involving mostly squamosal; incisive foramen
      approximately 5.5 × 2.7 mm, widest in anterior third and
      constricted posteriorly, with posterior margin about 1 mm anterior
      to plane of premolars; vomerine sheath complete, with premaxillary
      part expanded and maxillary part notably slender and sometimes
      lacking; mesopterygoid fossa in some specimens extending forward
      as far as middle parts of second molars; bullae large and
      inflated.

      _Teeth._--Upper molariform teeth with three counterfolds each.
      Lower premolar with three counterfolds; molars with only two.

      _Comparisons._--From _P. g. warreni_, _arabupu_ differs in:
      Narrower aristiforms; narrower incisive foramen; lower premolar
      with three instead of four counterfolds; lower molars with two,
      instead of three, counterfolds. From _P. g. oris_, _arabupu_
      differs in: Aristiforms wider; posterior margin of incisive
      foramen farther from plane of premolars; upper parts dark (15'_j_)
      Ochraceous-Tawny, instead of Ochraceous-Orange.

_Remarks._--The sample is fairly uniform.

      _Specimens examined._--Total number, 6 (AMNH), from Brazil,
      Territorio do Rio Branco, Bõa Vista, Mount Roraima, Arabupu;
      approximately 1540 m. altitude.


Subgenus =TRINOMYS= Thomas

      _Genotype._--_Echimys albispinus_ Is. Geoffroy Saint-Hilaire, 1838;
      by original designation.

      _Trinomys_ Thomas, July 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):140
      (orig. descr.); Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):401; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:115.

[Illustration: FIG. 99. Map showing the geographic ranges of the
subspecies of three species of the subgenus _Trinomys_.]

      _General characters._--Pelage of upper parts with lanceolate and,
      sometimes, clavate aristiforms extending over most of rump and onto
      thighs; tail 86 to 103 per cent of length of head and body; tail
      sometimes white-tipped and sometimes penicillate; skull small, with
      ridges moderately developed; supraorbital ridges involving no part
      of parietals; infraorbital foramen with no separate groove for
      transmission of nerve; mesopterygoid fossa extending forward to
      level of second or first molars; incisors opisthodont, orthodont or
      proodont; molariform teeth, in occlusal view, with main fold large
      and usually reaching opposite wall; no counterfold anterior to main
      fold in upper molariform teeth and usually no counterfold posterior
      to main fold in lower molariform teeth; premolars larger than first
      molars, first molars larger than second molars and second molars
      larger than third molars; four molariform teeth of nearly equal
      size in some animals.

      Thomas (1921:140) erected the subgenus _Trinomys_, including in it
      the species _albispinus_ and _setosus_ and stated that "the primary
      distinction between these [_Trinomys_ and _Proechimys_] lies in the
      number of laminae present in the cheekteeth--four in _Proechimys_,
      three in _Trinomys_." The distinction is valueless as a subgeneric
      character, not only because the character is not constant in the
      species in the subgenus but also because there is subspecific
      variation in number of laminae in the cheekteeth. _Proechimys
      albispinus_, however, shares with three other species common
      characters, as listed above, and the name _Trinomys_ will,
      therefore, apply to this group of species, since _Proechimys
      albispinus_ is the genotype.


=Proechimys dimidiatus= (Günther)

      _Echimys dimidiatus_ Günther, 1 April 1877, Proc. Zool. Soc.
      London, 1876(4):747.

      _Proechimys dimidiatus_ Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):264; Ribeiro, 1905, Arch. Mus. Nac. Rio de Janeiro, 13:187;
      Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):141; Tate, 1935,
      Bull. Amer. Mus. Nat. Hist., 68(5):400; Ellerman, 1940, The
      families and genera of living rodents, Brit. Mus. (Nat. Hist.),
      1:122.

      _Type locality._--Unknown; probably southwestern Rio de Janeiro,
      Brazil (see Remarks). _Type_: British Museum (Nat. Hist.), no.
      51.7.21.24; presented by Lord Derby.

      _Range._--Rio de Janeiro, from the southern limit of the state
      northward to and including the Distrito Federal.

      _General characters._--Size large; tail averaging 80 per cent of
      head and body; aristiforms narrow and soft (0.4 to 0.5 mm wide),
      imparting a non-spiny character to the pelage; general color of
      upper parts Ochraceous-Buff, finely lined with blackish brown,
      gradually becoming lighter on sides; ventral surface of body and
      inner sides of legs white; feet dorsally white but with a
      sepia-colored stripe along outer margin; tail brownish-black above
      and white below, but white sometimes extended to upper side in
      distal part; skull broad with no conspicuous ridges; jugals deep
      with transverse ridge usually conspicuous; postorbital process of
      zygoma involving only squamosal; incisive foramen short and wide
      posteriorly; vomerine sheath complete in 95 per cent of specimens
      and with maxillary part thick; posterior palatine foramina at
      plane of first molars or slightly anterior to them; bullae
      moderately developed; in juvenal specimens, each upper molariform
      tooth with three counterfolds, but posteriormost counterfold
      small; in adult specimens, posteriormost counterfold
      disappearing in 50 per cent of fourth premolars and first molars,
      in 20 per cent of second molars, and in 15 per cent of third
      molars; lower molariform teeth with two counterfolds in almost
      every juvenal specimen, this number, in adult animals, decreasing
      in m3 to one in 20 per cent of specimens but rarely being reduced
      in other teeth.

      _General characters._--Aristiforms soft and narrow, ranging from 15
      to 19 mm in total length and 0.4 to 0.5 mm in maximum width; pelage
      generally non-spiny and not harsh; length of tail ranging from 20
      per cent shorter than head and body to as long as, or slightly
      longer than, head and body; ears rather small (23 to 25 mm).

[Illustration: FIGS. 100-103. _Proechimys dimidiatus_, male, MN no.
5452, Tijuca. × 1.]

      _Color._--General color of back and sides results from uniform
      mixture of black distal parts of aristiforms with Ochraceous-Buff
      of subapical zone of setiforms. Dorsally, from nose caudad to rump,
      mixture appears brownish-black, lined with Ochraceous-Buff; toward
      sides, amount of Ochraceous-Buff gradually increases and resultant
      color is much lighter brown than on back. On outer parts of arms
      and legs, color turns gradually to sepia toward distal parts and
      finally to uniform sepia on wrists and ankles, this color extending
      to outer dorsal parts of hands and feet; on ankles, sepia forms
      complete ring, as usual in the genus. Tail blackish-brown on upper
      parts, this stripe gradually tapering toward tip where dark brown
      hairs form small pencil; white of under side of tail sometimes seen
      also entirely around distal part, short of tip which remains dark
      brown. Ventral surfaces wholly white, from upper lips caudad
      including inner surfaces of legs.

      _Hairs._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip that has long, fine filament;
      total length 16 to 19 mm; maximum width 0.5 mm. On outer thigh
      whitish basally, gradually blackening toward tip; some with
      Ochraceous-Buff, subapical zone; total length 13 to
      15 mm; maximum width 0.25 mm. _Setiforms on middorsal region_:
      Whitish on basal half, gradually blackening toward tip, but
      interrupted by Ochraceous-Buff, subapical zone; some with Light
      Ochraceous-Buff, subapical zone and short, blackish zone on tip;
      total length 12 to 14 mm; maximum width 0.02 mm. _Setiforms on
      outer thighs_: Whitish on basal half, then gradually becoming gray
      on middle part and finally Light Ochraceous-Buff on distal third,
      or with tip blackish and Ochraceous-Buff, subapical zone.

      _Skull._--Elongate and broad with no conspicuous crests; rostrum
      rather stout; jugals deep with transverse crest usually
      well-developed; zygomatic postorbital process conspicuous and
      formed entirely of squamosal; incisive foramen short and wide
      posteriorly; vomerine sheath complete in great majority of
      specimens, its maxillary part wide and strong; posterior palatine
      foramina on plane with front of M1 or slightly farther forward;
      bullae rather small and elongate.

      _Teeth._--P4 with three secondary folds in all juvenal specimens,
      but posteriormost fold small and disappearing in 50 per cent of
      adult specimens; M1 with 3 outer folds in juveniles and also
      disappearing in 50 per cent of adults; M2 with three outer folds
      in juveniles, but only 20 per cent remaining in adults; M3 with 3
      outer folds in 50 per cent of juveniles, decreasing to 15 per cent
      in adults. Lower molariform teeth: p4 with 2 secondary folds; m1
      with 2 secondary folds in 90 per cent of adults and in all
      juveniles; m2 with 2 secondary folds in 98 per cent of adults and
      in all juveniles; m3 with 2 secondary folds in 81 per cent of
      adults, remaining percentage with only one counterfold, and with 2
      secondary folds in all juveniles.

_Remarks._--Samples studied of _P. dimidiatus_ are notably uniform
throughout the geographic range of the species. The few biotypes
detected seemed unworthy of subspecific rank.

In discussing the type locality of the species, Thomas (1921:141)
states: "We know that its donor did obtain a number of specimens from
Rio Janeiro, and the skull agrees so closely with those of two examples
from Itatiaia, near to the Rio-Minas frontier, collected and presented
by Prof. J. P. Hill, that I have no hesitation in referring the latter
to Günther's species."

      _Specimens examined._--Total number, 211 (MN), from Brazil as
      follows: Rio de Janeiro; _Parati_, Pedra Branca (400 m.), 113;
      _Mangaratiba_, Fazenda do Rubião (750 m.), 3; Fazenda do Tenente
      (700 m.), 4; Fazenda da Lapa (450 m.), 13; _Teresópolis_, Fazenda
      Guinle (960 m.), 61; _Nova Iguassú_, Barro Branco (20 m.), 16;
      Distrito Federal, Tijuca, 1.

      _Additional records._--Rio de Janeiro, Itatiaia (Thomas,
      1921:141); Rio de Janeiro, Zona da mata, Mont-Serrat, Serra do
      Itatiaia (Ribeiro, 1905:187).


=Proechimys iheringi= Thomas

      _General characters._--Size large; tail long; aristiforms generally
      wide and stiff; general color on upper parts and sides a
      combination of blackish from tips of aristiforms with cinnamon
      ground color from subapical zones of setiforms; darker band on
      middorsal line; differentiated light-colored aristiforms
      conspicuous on outer sides of thighs and rump; usually rufous tint
      on neck and postauricular region; underparts white; tail with white
      tip, usually accentuated by white brush; feet white on dorsal
      surface; hind feet slightly darker on outer sides; skull elongate
      and smooth; jugals wide dorso-ventrally; incisive foramen elongate;
      upper molariform teeth usually with one to five counterfolds, number
      varying with subspecies; lower premolar always with two counterfolds
      and lower molars always with one or two counterfolds.

_Remarks._--As a whole, the samples of the populations of the species do
not afford a satisfactory record of the distribution; my concept of the
group may be changed when further collections are made in localities
geographically intermediate between those from which specimens now are
known. If some of the forms prove to be physiologically isolated, they
may deserve treatment as full species according to the conventional
standards of systematic zoology. _P. panema_, for example, does not seem
to be geographically isolated from _P. gratiosus_. _P. denigratus_, at
the northernmost known occurrence of the species, actually represents a
striking jump in the cline, although collections from intermediate
regions may provide intermediate structural stages. Further collecting
may also prove that the southern form, _P. iheringi iheringi_, is
completely isolated from the rest of the group. However, these samples
are certainly more related to each other than any one of them is to that
of the other species found in the same range, namely _P. dimidiatus_,
and all the forms in question, therefore, seem best arranged as
subspecies of one full species. A clinal variation certainly exists
among these forms and the most striking differences correspond to larger
geographical distances.

[Illustration: FIG. 104. _Proechimys iheringi iheringi_, female, MN no.
6453, Ilha de São Sebastião. × 1.]

[Illustration: FIG. 105. _Proechimys iheringi bonafidei_, male, MN no.
6183, Fazenda Bõa Fé. Type. × 1.]

[Illustration: FIG. 106. _Proechimys iheringi gratiosus_, male, MN no.
4024, Floresta da Caixa Dagua. Type. × 1.]

[Illustration: FIG. 107. _Proechimys iheringi panema_, female, MN no.
8288, Campinho. Type. × 1.]

[Illustration: FIG. 108. _Proechimys iheringi denigratus_, male, MN no.
8500, Mata do Ribeirão da Fortuna. Type. × 1.]

[Illustration: FIG. 109. _Proechimys iheringi paratus_, female, MN no.
4012, Floresta da Capela de São Braz. Type. × 1.]

[Illustration: FIG. 110. _Proechimys iheringi iheringi_, female, MN no.
6453, Ilha de São Sebastião. × 1.]

[Illustration: FIG. 111. _Proechimys iheringi bonafidei_, male, MN no.
6183, Fazenda Bõa Fé. Type. × 1.]

[Illustration: FIG. 112. _Proechimys iheringi gratiosus_, male, MN no.
4024, Floresta da Caixa Dagua. Type. × 1.]

[Illustration: FIG. 113. _Proechimys iheringi panema_, female, MN no.
8288, Campinho. Type. × 1.]

[Illustration: FIG. 114. _Proechimys iheringi denigratus_, male, MN no.
8500, Mata do Ribeirão da Fortuna. Type. × 1.]

[Illustration: FIG. 115. _Proechimys iheringi paratus_, female, MN no.
4012, Floresta da Capela de São Braz. Type. × 1.]

[Illustration: FIGS. 116, 117. _Proechimys iheringi iheringi_, female,
MN no. 6453, Ilha de São Sebastião. × 1.]

[Illustration: FIGS. 118, 119. _Proechimys iheringi bonafidei_, male, MN
no. 6183, Fazenda Bõa Fé. Type. × 1.]

[Illustration: FIGS. 120, 121. _Proechimys iheringi gratiosus_, male, MN
no. 4024, Floresta da Caixa Dagua. Type. × 1.]

[Illustration: FIGS. 122, 123. _Proechimys iheringi panema_, female, MN
no. 8288, Campinho. Type. × 1.]

[Illustration: FIGS. 124, 125. _Proechimys iheringi denigratus_, male,
MN no. 8500, Mata do Ribeirão da Fortuna. Type. × 1.]

[Illustration: FIGS. 126, 127. _Proechimys iheringi paratus_, female, MN
no. 4012, Floresta da Capela de São Braz. Type. × 1.]


=Proechimys iheringi iheringi= Thomas

      _Proechimys iheringi_ Thomas, August, 1911, Ann. Mag. Nat. Hist., 8
      (ser. 8):252 (orig. descr.); Thomas, 1921, Ann. Mag. Nat. Hist., 8
      (ser. 9):141; Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400;
      Ellerman, 1940, The families and genera of living rodents, Brit.
      Mus. (Nat. Hist.), 1:122.

      _Type locality._--Island of São Sebastião (off São Paulo), Formosa,
      São Paulo, Brazil. _Type_: British Museum (Nat. Hist.), no.
      2.8.25.5, adult male, presented by the São Paulo Museum.

      _Range._--Littoral and islands of São Paulo and Rio de Janeiro.

      _Diagnosis._--Aristiforms narrow; tail shorter than head and body;
      setiforms Cinnamon-Buff; incisive foramen short; vomerine sheath
      complete; upper molariform teeth with two or three counterfolds;
      lower molariform teeth with two counterfolds, rarely one in m3.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length 18 to 23 mm; maximum
      width, 0.6 mm. _Aristiforms on outer thighs_: Gray basally,
      blackening distally toward tip; some differentiated with
      Cinnamon-Buff tip. _Setiforms on middorsal region_: Gray basally,
      gradually blackening toward tip but interrupted by a
      Cinnamon-Buff, subapical zone 3 mm long; total length, 16 to 20
      mm; maximum width, 0.06 mm. _Setiforms on outer thighs_: Gray
      basally, gradually blackening toward tip but interrupted by
      Cinnamon-Buff, subapical zone or with Cinnamon-Buff continuous to
      tip.

      _Skull._--Slender; bullae small and well inflated; jugal
      dorso-ventrally wide with transverse ridge inconspicuous; incisive
      foramen short, 3.5 × 2.5 mm; vomerine sheath complete;
      mesopterygoid fossa extending forward as far as middle parts of
      second molars; postorbital process of zygoma small, formed by both
      jugal and squamosal; posterior palatine foramina at plane of
      premolars; interorbital breadth narrow.

      _Teeth._--Upper molariform teeth with two or three counterfolds
      (when unworn usually three and rarely four); sometimes only one
      counterfold in M3 and sometimes counterfolds fused in molars.
      Lower molariform teeth with two counterfolds, rarely one in m3.

      _Comparisons._--From _P. i. bonafidei_ and _P. i. gratiosus_,
      _iheringi_ differs in: Incisive foramen shorter; vomerine sheath
      complete, instead of usually incomplete; setiforms Cinnamon-Buff,
      instead of Ochraceous-Buff; upper molariform teeth with two or
      three separate counterfolds, instead of having counterfolds fused
      or reduced to one or two; aristiforms narrower in _iheringi_ than
      in _bonafidei_.

      _Specimens examined._--Total number, 25, from Brazil, as follows:
      São Paulo, _Formosa_, Ilha de São Sebastião, 9 (DZ 6, MN 2, MCZ 1);
      São Paulo, _Mogi das Cruzes_, Alto da Serra, alt. 900 m., 2 (DZ);
      São Paulo, _Ubatuba_, alt. 10 m., 4 (2 DZ, 2 MN); Rio de Janeiro,
      _Angra dos Reis_, 2 (MN); Rio de Janeiro, _Angra dos Reis_, Ilha
      Grande, 7 (5 DZ, 1 MCZ, 1 MN).


=Proechimys iheringi bonafidei= subspecies nova

      _Type locality._--Fazenda Bõa Fé, _Teresópolis_, Rio de Janeiro,
      Brazil; alt. 850 meters. _Type_: Museu Nacional, no. 6183, adult
      male; collected on 18 August, 1942, by G. Pereira; SEPFA no. M
      14663.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms wide and stiff; tail shorter than head
      and body; setiforms Ochraceous-Buff; incisive foramen long;
      vomerine sheath incomplete, or rarely complete; molariform teeth
      with two counterfolds usually fused.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 22 to 26 mm;
      maximum width, 0.8 mm. _Aristiforms on outer thighs_: Gray
      basally, gradually blackening toward tip but interrupted by
      Ochraceous-Buff subapical zone; some Ochraceous-Buff to tip; total
      length, 18 to 20 mm; maximum width, 0.7 mm. _Setiforms on
      middorsal region_: Gray basally, gradually blackening toward tip
      but interrupted by Ochraceous-Buff, subapical zone; total length,
      17 to 20 mm; maximum width, 0.06 mm. _Setiforms on outer thighs_:
      Gray basally, gradually blackening toward tip but interrupted by
      Ochraceous-Buff, subapical zone; only a short blackened tip.

      _Skull._--Large, with elongate rostrum; bullae large and well
      inflated; jugals with transverse ridge inconspicuous; postorbital
      process of zygoma small, formed mostly by squamosal; incisive
      foramen elongated (5.5 × 2.5 mm); vomerine sheath incomplete or,
      if complete, with maxillary part thin and delicate; posterior
      palatine foramen at plane of first molars; mesopterygoid fossa
      extending forward as far as middle parts of second molars.

      _Teeth._--Upper molariform teeth with two counterfolds; these
      completely separated in 3 of 16 specimens; two counterfolds
      coalesced in all three molars in 6 specimens; counterfolds
      coalesced in only two molars in 3 specimens; counterfolds
      coalesced in only one molar in 4 specimens. Lower molariform teeth
      with two counterfolds which are completely separated in 13 of 16
      specimens; counterfolds coalesced in only one molar in 2
      specimens; counterfolds coalesced in all three molars in one
      specimen.

      _Comparisons._--From _P. i. gratiosus_, _bonafidei_ differs in:
      Aristiforms wider; tail shorter; molariform teeth with two
      counterfolds instead of one or two. Differences from _P. i.
      iheringi_ are given in the account of that subspecies.

_Remarks._--Of females with embryos two were captured in April and one
in September. The embryos number 2, 1, 2. Young were captured mostly in
April, but two were taken in July. Male gonads seemed to be most active
in March, April and September. The animals lived in a second growth
forest, approaching the climax. The rainfall was more than 1600 mm
annually, and the mean annual temperature was 18.5° centigrade.

      _Specimens examined._--Total number, 18 (MN), from Brazil, Rio de
      Janeiro, _Teresópolis_, Fazenda Bõa Fé.


=Proechimys iheringi gratiosus= subspecies nova

      _Type locality._--Floresta da Caixa Dagua, _Santa Teresa_, Espirito
      Santo, Brazil; altitude 750 meters. _Type_: Museu Nacional, no.
      4024, adult male; collected on 25 May, 1940, by C. Lako; SEPFA no.
      M 6911.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms narrow; tail of same length as head and
      body; setiforms Ochraceous-Buff; incisive foramen long; vomerine
      sheath usually incomplete; upper molariform teeth with one or two
      counterfolds; lower molariform teeth with two counterfolds, except
      that m3 usually has only one.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 21 to 27 mm; maximum
      width, 0.6 mm. _Aristiforms on outer thighs_: Gray basally,
      gradually blackening toward middle, and Ochraceous-Buff on distal
      half; total length, 18 to 21 mm; maximum width, 0.5 mm. _Setiforms
      on middorsal region_: Gray basally, gradually blackening toward tip
      but interrupted by short, Ochraceous-Buff, subapical zone; total
      length, 18 to 20 mm; maximum width, 0.06 mm. _Setiforms on outer
      thighs_: Gray basally, gradually blackening toward middle, and
      distal part Ochraceous-Buff or with only tip blackened; total
      length, 14 to 16 mm; maximum width, 0.05 mm.

      _Skull._--Slender; bullae small but well-inflated; upper edge of
      jugals deeply concave; transverse ridge of jugals conspicuous;
      postorbital process of zygoma small, involving only squamosal;
      incisive foramen elongate (5 x 2.5 mm); vomerine sheath almost
      always incomplete, and maxillary part lacking or, when present,
      slender; mesopterygoid fossa extending forward as far as middle of
      second molars; posterior palatine foramina at plane of front
      border of first molars or slightly anterior thereto.

      _Teeth._--Upper molariform teeth with two counterfolds in 10 of 16
      specimens and only one in remainder; these folds commonly
      coalesced; M3 with only one counterfold in 6 specimens, and 2
      counterfolds in remainder. Lower molariform teeth with two
      counterfolds in 6 specimens and in 10 of them m3 has only one
      counterfold.

      _Comparisons._--From _P. i. panema_, _gratiosus_ differs in: Lower
      molariform teeth with only one counterfold in smaller percentage
      of specimens; incisive foramen shorter; aristiforms narrower;
      setiforms Ochraceous-Buff instead of Cinnamon. Differences from
      _iheringi_ and _paratus_ are given in the accounts of those
      subspecies.

_Remarks._--All the animals were captured in climax forest.

      _Specimens examined._--Total number, 16 (MN), from Brazil, Espirito
      Santo, _Santa Teresa_, Floresta da Caixa Dagua, altitude 750
      meters.


=Proechimys iheringi panema= subspecies nova

      _Type locality._--Campinho, _Colatina_, Espirito Santo, Brazil;
      altitude 500 meters. _Type_: Museu Nacional, no. 8288, adult
      female; collected on 15 July, 1942, by C. Lako.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms moderately wide; tail of approximately
      same length as head and body; setiforms Cinnamon; incisive foramen
      moderately long and narrow; vomerine sheath incomplete; upper
      molariform teeth with two counterfolds, but m3 most frequently
      with one.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 21 to 23 mm;
      maximum width, 0.8 mm. _Aristiforms on outer thighs_: Gray, some
      gradually blackening toward tip and others with distal part
      Cinnamon; total length, 17 to 19 mm; maximum width, 0.7 mm.
      _Setiforms on middorsal region_: Gray, gradually blackening
      toward tip, but interrupted by Cinnamon, subapical zone; total
      length, 18 to 20 mm; maximum width, 0.06 mm. _Setiforms on outer
      thighs_: Gray, gradually blackening toward middle, and Cinnamon on
      all of distal parts or with tip blackish; total length, 13 to 15
      mm; maximum width, 0.09 mm.

      _Skull._--Strong, with jugals dorso-ventrally wide; interorbital
      region and cranium wide; bullae well inflated; transverse ridge of
      jugals not well-developed; postorbital process of zygoma small and
      formed only of squamosal; incisive foramen 4.7 × 2.2 mm; vomerine
      sheath always incomplete, with maxillary part reduced to small
      process; mesopterygoid fossa extending forward as far as middle of
      second molars or only slightly short thereof; posterior palatine
      foramina at plane of front of first molars.

      _Teeth._--All upper molariform teeth with two counterfolds in 4
      specimens; one having only one counterfold in M3; 3 with
      counterfolds coalesced in one or two molars. Lower molariform
      teeth with two counterfolds in one specimen, these counterfolds
      not coalesced; m3 with one counterfold in 4 specimens and with two
      in one specimen.

      _Comparisons._--Differences from _P. denigratus_ and _P. i.
      paratus_ are given in the accounts of those animals.

      _Specimens examined._--Total number, 5 (MN), from Brazil, Espirito
      Santo, _Colatina_, Campinho; altitude 500 meters.


=Proechimys iheringi denigratus= subspecies nova

      _Type locality._--Mata do Ribeirão da Fortuna, 40 kilometers west
      of Ilheus, _Itabuna_, Bahia, Brazil. _Type_: Museu Nacional, no.
      8500, adult male; collected 16 March, 1945.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms wide and stiff; tail longer than head
      and body; setiforms near (15''_a_) Cinnamon; incisive foramen long
      and narrow; vomerine sheath complete; premolars with two
      counterfolds, upper molars with one or two, and lower molars with
      only one.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 20 to 22 mm;
      maximum width, 1.1 mm. _Aristiforms on outer thighs_: Gray
      basally, gradually blackening toward tip or with distal part near
      (15''_a_) Cinnamon; total length, 14 to 16 mm; maximum width, 0.5
      mm. _Setiforms on middorsal region_: Gray basally, gradually
      blackening toward tip but interrupted by near (15''_a_) Cinnamon,
      subapical zone 4 mm wide; total length, 18 to 20 mm; maximum
      width, 0.05 mm. _Setiforms on outer thighs_: Gray basally,
      gradually blackening toward tip but interrupted by wide, near
      (15''_a_) Cinnamon, subapical zone.

      _Skull._--Slender; nasals short; bullae large and well-inflated;
      jugals with conspicuous transverse ridge; postorbital process of
      zygoma conspicuous, spiniform and formed almost exclusively by
      jugal; incisive foramen elongated and narrow (5 × 1.8 mm);
      vomerine sheath complete and formed almost exclusively by
      premaxillae; maxillary part of this sheath short and in most
      specimens the two parts of sheath completed by vomer itself;
      mesopterygoid fossa extending forward as far as middle of second
      molars and in some skulls as far as anterior border of second
      molars; posterior palatine foramina at anterior plane of first
      molars.

      _Teeth._--Upper molariform teeth: P4 always with two counterfolds;
      M1 with two counterfolds in 65 per cent of specimens but anterior
      counterfold poorly developed; rest of specimens with only one
      counterfold in M1; M2 with two counterfolds in 50 per cent of
      specimens and only one in remainder; M3 with two counterfolds in
      only 17 per cent of specimens, and remainder with only one. Lower
      molariform teeth: p4 always with two counterfolds; molars always
      with only one counterfold.

      _Comparisons._--From _P. i. panema_, _denigratus_ differs in: Each
      lower molar with only one, instead of with more than one,
      counterfold; incisive foramen longer and narrower; vomerine sheath
      complete instead of incomplete; aristiforms conspicuously wider;
      tail longer.

_Remarks._--One female (SEPFA no. M 17060) captured on 9 January, 1944,
gave birth to two females on 26 January, 1944. Each of these young
measured 177 mm in total length and weighed 27.8 g. On 4 March, 1944,
their measurements were: head and body, 120,120; tail, 120,130; hind
foot, 32,33; ear, 21,22; skull:--total length, 36.0,35.0;
condyloincisive length, 29.0,29.1; zygomatic breadth, 19.1,18.5; length
of nasals, 12.5,11.6; interorbital constriction, 9.3,8.8; cranial
breadth, 16.4,16.9; palatilar length, 11.5,10.5; crown length of P4 and
M1, 4.3,4.3 mm.

The forest where the animals were captured has a high percentage of
deciduous trees in spite of the heavy rainfall in this region. All of
the animals were trapped near water. Young were captured from January to
May. Most animals have a conspicuous Cinnamon patch on the nuchal
region.

      _Specimens examined._--Total number, 34 (SEPFA 33, MN 1), from
      Brazil, Bahia, _Itabuna_, Mata do Ribeirão da Fortuna.


=Proechimys iheringi paratus= subspecies nova

      _Type locality._--Floresta da Capela de São Braz, _Santa Teresa_,
      Espirito Santo, Brazil; altitude 630 meters. _Type_: Museu
      Nacional, no. 4012, adult female; collected on 24 September, 1940,
      by Dr. H. W. Laemmert; SEPFA no. M 8447.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms wide and stiff; tail 96 per cent of head
      and body; color on setiform Cinnamon-Buff; incisive foramen short
      and moderately wide; vomerine sheath complete; all molariform
      teeth with two counterfolds.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 24 to 26 mm;
      maximum width, 1.3 mm. _Aristiforms on outer thighs_: Gray
      basally, gradually blackening toward middle, and distal parts near
      (15''_c_) Pinkish Cinnamon; total length, 18 to 20 mm; maximum
      width 0.8 mm. _Setiforms on middorsal region_: Gray basally,
      gradually blackening toward tip but interrupted by Cinnamon-Buff,
      subapical zone; total length 14 to 16 mm; maximum width, 0.06 mm.

      _Skull._--Slender; bullae large and well-inflated; jugals with
      conspicuous, transverse ridge; postorbital process of zygoma
      moderately developed and involving only squamosal; incisive
      foramen short and narrow (4.1 × 2.1 mm); vomerine sheath complete,
      with maxillary part short and thick; mesopterygoid fossa extending
      forward as far as posterior parts of second molars; posterior
      palatine foramina at plane of premolars.

[Illustration: FIG. 128. Map showing the geographic ranges of the
subspecies of _Proechimys iheringi_.]

      _Teeth._--Upper and lower molariform teeth with two counterfolds.
      Counterfolds coalesced in P4 and M1 of one specimen.

      _Comparisons._--From _P. i. gratiosus_ and _P. i. panema_,
      _paratus_ differs in: all molariform teeth with two, instead of
      some with fewer, counterfolds; vomerine sheath complete and thick
      instead of usually incomplete; incisive foramen shorter and
      narrower; aristiforms conspicuously wider; setiforms Cinnamon-Buff
      instead of Ochraceous-Buff and Cinnamon, respectively. Tail 96 per
      cent of head and body in _paratus_ instead of 100 per cent as in
      _panema_.

_Remarks._--The animals were captured in climax forest.

      _Specimens examined._--Total number, 3 (MN), from Brazil, Espirito
      Santo, _Santa Teresa_, Floresta da Capela de São Braz; altitude 630
      meters.


Proechimys setosus (Desmarest)

      _General characters._--Size medium; tail approximately same length
      as head and body; aristiforms moderately wide; feet rather large;
      ears of medium size; color on upper parts and sides sepia gradually
      changing to Ochraceous-Tawny; few differentiated, light-colored
      aristiforms present on outer thighs and rump; under surface of body
      and inner sides of legs white; tail with white tip and conspicuous,
      white pencil; feet white dorsally; skull short and smooth, somewhat
      flattened in interorbital region; jugals narrow dorso-ventrally;
      incisive foramen moderately long and notably narrow; vomerine
      sheath complete and slender; postorbital process of zygoma
      spinelike and involving mostly jugal; premolars usually with two
      counterfolds; molars with only one counterfold, rarely two in M1 or
      in M3.

_Remarks._--The specimens available are undoubtedly faded and,
therefore, the colors mentioned above for the upper parts and sides may
not correspond to the colors of unfaded pelages. Desmarest (1817:59)
describes the color of setosus as similar to that of the "Echimys de
Cayenne" (_Proechimys guyannensis_) but being more "rousse." Is.
Geoffroy Saint-Hilaire (1840:52) describes the same animal as being
"d'un brun roussâtre" on the upper parts.

The _Proechimys_ from Lagoa Santa, Minas Gerais, _"Echimys" elegans_
Lund, is certainly related to _P. iheringi_ as well as to _P.
albispinus_. From _P. iheringi_, _elegans_ differs in having a smaller
skull with shorter rostrum, narrower incisive foramen, and orthodont
incisors. On the other hand the restricted distribution of the
aristiforms in the pelage and the white, penicillate tail are points of
resemblance to _iheringi_. From _P. albispinus_, _elegans_ differs in
having a less spinous pelage and longer tail with white pencil instead
of a brown pencil. The skulls, however, are similar, except for the fact
that _elegans_ does not have proodont incisors as _albispinus_ sometimes
does. Thomas (1921:141) states, after describing the skull of the type
of _setosus_, that "Specimens corresponding to this animal have been
obtained at Lagoa Santa, Minas, by Lund and others, and at Bahia."
Thomas, however, would not have referred to specimens from "Bahia" as
being comparable to _elegans_ had they not been different from
_albispinus_ which he discussed in the same paper. Also, he would not
have confused "specimens comparable to _elegans_" with a subspecies of
_P. iheringi_ (_P. i. denigratus_, from southern Bahia) which has
opisthodont instead of orthodont incisors. Since French collectors sent
material to Europe at the beginning of the 19th century from (southern?)
Bahia, possibly _setosus_ came from there.

In the collection of the American Museum of Natural History there is one
specimen (AMNH no. 16140) of _Proechimys_, included in the so-called
Maximilian Collection. The characters of this specimen agree closely
with those of the specimens from Lagoa Santa. The locality of capture of
specimen no. 16140 is unknown, but it is reasonable to assume that
Prince Maximilian zu Wied obtained it somewhere along his route of
travel through southeastern Bahia. Wied (1826:445) mentions
"_L[oncheres]. myosuros_ Licht." as "am Parahyba, am Peruhype und
Belmonte," which greatly increases the possibility of its having come
from southern Bahia. The close similarity to _elegans_ of Wied's
specimen indicates that the locality of capture possibly was in the
region of the less humid, low escarpments of southern Bahia.

My conclusion is that Wied's specimen corresponds closely to _setosus_
and, tentatively, I identify it as such. "_Echimys elegans_," due to the
relationships mentioned above is here considered to be a subspecies of
_setosus_.

Among the species described in earlier times, and whose identity was
never ascertained, _"Echinomys" fuliginosus_ Wagner seems to be
synonymous with _setosus_. Wagner describes the animal as having a tail
"apicis versus pilis albidis vestita" and the figure of the cheekteeth
(1844, pl. 239 D) shows a typical trilaminate condition which occurs
commonly in _elegans_. Moreover, the tail of _fuliginosus_ is only 9 per
cent shorter than the head and body and the aristiforms of this
subspecies are moderately wide.


=Proechimys setosus setosus= (Desmarest)

      _Echimys setosus_ Desmarest (Geoffroy's MS), 1817, Nouv. Dict.
      Hist. Nat. nouv. ed., 10:59 (orig. descr.); Is. Geoffroy
      Saint-Hilaire, 1838, Comptes Rendus Acad. Sci., Paris, 6(26):886;
      Is. Geoffroy Saint-Hilaire, 1840, Mag. Zool., Paris, (ser. 2, année
      2):12, 33, 52; Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):257, 261.

      _Echimys cayennensis_ Pictet, 1841, Mém. Soc. phys. Hist. Nat.,
      Genève, 9:145; Waterhouse, 1848, Nat. Hist. Mammalia, 2:334.

      _Echinomys fuliginosus_ Wagner, 1843, Schreber's Säugethiere,
      suppl. 3:343; Wagner, 1844, Schreber's Säugethiere, suppl. 4, pl.
      39 D.

      _Proechimys setosus_ Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):264; Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):141;
      Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):401; Ellerman,
      1940, The families and genera of living rodents, Brit. Mus.
      (Nat. Hist.), 1:122.

      _Proechimys fuliginosus_ Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
       68(5): 400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _Type locality._--Unknown; see remarks under _P. setosus_. _Type_:
      Museum d'Histoire Naturelle, Paris, no. A. 7787 (Thomas, 1921:141),
      "very imperfect."

      _Diagnosis._--Aristiforms wide; P4 and M1 with two counterfolds;
      p4 with two counterfolds, one anterior to main fold.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 18 to 20 mm;
      maximum width, 0.8 mm. _Aristiforms on outer thighs_: Color much
      faded; total length, 15 to 17 mm; maximum width, 0.3 mm.
      _Setiforms on middorsal region_: Color faded; total length, 16 to
      18 mm; maximum width, 0.04 mm. _Setiforms on outer thighs_: Color
      faded; total length, 10 to 13 mm; maximum width, 0.03 mm.

[Illustration: FIGS. 129-132. _Proechimys setosus elegans_, sex ?, UZM
no. L 104, Lagoa Santa. × 1.]

      _Skull._--Short; rostrum short and stout; length of nasals
      approximately 15 mm (broken); bullae roundish, smooth and
      well-inflated; jugals dorso-ventrally narrow (3.1 mm) with strong
      transverse ridge; postorbital process of zygoma spiniform, slender
      and involving mostly jugal; incisive foramen narrow (3.8 x 1.7 mm)
      and narrowest in posterior part; vomerine sheath complete;
      posterior palatine foramina obsolete; mesopterygoid fossa extending
      forward as far as middle of second molars.

      _Teeth._--Incisors orthodont. P4 with two counterfolds; M1 with
      two counterfolds but anterior one notably small; M2 and M3 with
      only one counterfold each. In lower jaw: p4 with two counterfolds,
      one anterior to main fold; molars with only one counterfold.

      _Comparisons._--From _P. s. elegans_, _setosus_ differs in: M1 with
      two counterfolds as opposed to only one; M3 with one counterfold
      instead of sometimes with two counterfolds; p4 with one counterfold
      anterior to main fold and another posterior, instead of both
      counterfolds posterior.

_Remarks._--The measurements above were taken from the Maximilian
specimen mentioned above. Measurements of the type were given by
Desmarest as: head and body, 5-1/2 inches, tail about 6-1/2 inches. Is.
Geoffroy Saint-Hilaire (1838:886) corrects these measurements to: head
and body 195 mm; tail (part missing), 170 mm.


=Proechimys setosus elegans= (Lund)

      _E[chimys]. elegans_ Lund, 1841, Kong. Danske Videnskab. Selsk.
      natur-vidensk. math. Afhandl., Kjöbenhavn, 8:99 (orig. descr.).

      _Loncheres elegans_ Lund, 1841, Kong. Danske Videnskab. Selsk,
      natur-vidensk. math. Afhandl., Kjöbenhavn, 8:245, 266, 294;
      Wagner, 1843, Wiegman's Archiv f. Naturg., Berlin, 2 (Jahrg.
      9):47.

      _Echimys cayennensis_ Waterhouse, 1848, Nat. Hist., Mammalia,
      2:337.

      _Echinomys cajennensis_ Winge, 1888, Jordfundne og nulevende
      Gnavere (Rodentia), E Museo Lundii, Kjöbenhavn, 1(3):71,
      pl. 6, figs. 5-6, pl. 7, fig. 1.

      _Proechimys setosus_ Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser.
      9):141.

      _Proechimys elegans_ Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _Type locality._--Lagoa Santa, _Nova Lima_, Minas Gerais, Brazil.
      _Type_: Syntypes in Universitets Zoologiske Museum, Kjöbenhavn;
      collected by P. W. Lund.

      _Range._--Known only from the type locality.

      _Diagnosis._--Aristiforms wide; P4 usually with two counterfolds;
      M3 sometimes with two counterfolds; p4 with two counterfolds
      anterior to main fold.

      _Pelage._--_Aristiforms on middorsal region_: Gray basally,
      gradually blackening toward tip; total length, 18 to 20 mm;
      maximum width, 0.7 mm. _Aristiforms on outer thighs_: Gray
      basally, gradually blackening toward tip which is Cinnamon; total
      length, 15 to 17 mm; maximum width, 0.3 mm. _Setiforms on
      middorsal region_: Whitish basally, gradually blackening toward
      tip, but interrupted by Cinnamon, subapical zone; total length, 17
      to 19 mm; maximum width, 0.04 mm. _Setiforms on outer thighs_:
      Whitish basally, gradually blackening toward tip but interrupted
      by near (15''_a_) Cinnamon, subapical zone; total length, 10 to 12
      mm; maximum width, 0.03 mm.

      _Skull._--Short; rostrum short but not stout; length of nasals 17
      mm; bullae large, smooth, and well-inflated; jugals with
      conspicuous, transverse ridge; postorbital process of zygoma long,
      spiniform and constructed entirely of jugal; incisive foramen
      narrow (4 × 1.7 mm); vomerine sheath complete and slender;
      posterior palatine foramina obsolete; mesopterygoid fossa
      extending anteriorly as far as middle parts of second molars.

      _Teeth._--Incisors orthodont. P4 usually with two counterfolds,
      rarely with three; upper molars with only one counterfold, but M3
      sometimes with two, posterior one being vestigial. Lower
      molariform teeth: p4 with two counterfolds, both being anterior to
      main fold; molars with only one counterfold.

      _Comparisons._--Differences from _P. s. setosus_ are given in the
      account of that subspecies.

_Remarks._--According to Lund, these animals are found in the vicinity
of small pools, swim well in spite of not having webbed toes, at night
go after food and climb the corn stalks, and have their nests in the
grass at the margins of the pools.

      _Specimens examined._--Total number, 2 (UZM), from Brazil, Minas
      Gerais, _Nova Lima_, Lagoa Santa.


=Proechimys albispinus= (Is. Geoffroy)

      _General characters._--Size small; tail of same length as head and
      body or slightly less; feet small; ears of medium size; color of
      upper parts Ochraceous-Tawny gradually changing to Ochraceous-Buff
      on sides; differentiated, light-colored aristiforms on back, sides,
      rump and at base of tail; clavate aristiforms on back with
      Ochraceous-Tawny or Ochraceous-Buff, subapical zone; underparts of
      body and inner sides of legs white; tail blackish above, white
      below, with no white tip; hands and feet white on dorsal parts and
      some specimens darker on outer margins of feet; skull short and
      smooth, somewhat flattened in frontal region; jugal dorso-ventrally
      wide and with moderately conspicuous transverse ridge; postorbital
      process of zygoma well developed and involving both jugal and
      squamosal; bullae large and smooth; incisive foramen short and
      narrow; vomerine sheath incomplete or complete; molariform teeth
      with only one counterfold; incisors orthodont or proodont.

_Remarks._--A good series from Macaco Seco, Andaraí, Bahia, agrees
closely with the form first described (_albispinus_) from the Island
Madre de Deus, in Todos os Santos Bay, Bahia. Compared with topotypes of
_P. albispinus sertonius_, the animal from Macaco Seco in general color
is more Ochraceous-Tawny and has a narrower skull with orthodont
incisors. Specimens from Bonfim, northeastern Bahia, on the other hand,
agree with Thomas' _albispinus sertonius_, from Lamarão, being browner
and having broader skulls than _P. a. albispinus_ and having proodont,
instead of orthodont, incisors. The range of each of the two subspecies
is, therefore, fairly extensive. The insular form extends to the less
rainy, continental area and the form from Lamarão ranges northward (NNW)
in the same type of highly deciduous forest, the "caatinga."

The species _albispinus_ is certainly the most specialized form of the
entire genus for drier habitats. In addition to the general adaptations
described above, it is noteworthy for having both lanceolate and clavate
aristiforms. The latter type has a wide basal part and an abruptly
narrowed, distal part. The same development is seen in the genus
_Echimys_, where highly spinous forms, like _Echimys paleacea_
(Lichtenstein), show the same two types of aristiforms.

[Illustration: FIGS. 133, 135. _Proechimys albispinus albispinus_, male,
CNHM no. 20409, Macaco Seco. × 1.]

[Illustration: FIGS. 134, 136. _Proechimys albispinus sertonius_, male,
MN no. 6454, Bonfim. × 1.]

[Illustration: FIGS. 137, 138. _Proechimys albispinus albispinus_, male,
CNHM no. 20409, Macaco Seco. × 1.]

[Illustration: FIGS. 139, 140. _Proechimys albispinus sertonius_, male,
MN no. 6454, Bonfim. × 1.]


=Proechimys albispinus albispinus= (Is. Geoffroy)

      _Echimys albispinus_ Is. Geoffroy Saint-Hilaire, 25 June 1838,
      Comptes Rendus Acad. Sci., Paris, 6(26):886; Is. Geoffroy, August,
      1838, Ann. Sci. Nat., Paris, 10 (ser. 2):125; Is. Geoffroy,
      1840, Mag. Zool., Paris (ser. 2, année 2, livr. 13):33, 53, pl. 26,
      pl. 29 (figs. 1, 2, 3); Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):261.

      _Echinomys fuliginosus_ Wagner, 1843, Schreber's Säugethiere,
      suppl., 3:343.

      _Echimys albispinosus_ Waterhouse, Nat. Hist., Mammalia, 2:341.

      _Proechimys albispinus_ Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):264; Thomas, 1911, Ann. Mag. Nat. Hist., 8 (ser. 8):252.

      _Proechimys albispinus albispinus_ Thomas, 1921, Ann. Mag. Nat.
      Hist., 8 (ser. 9):141; Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):401; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:122.

      _Type locality._--Ilha Madre de Deus, _Itaparica_ (near Salvador),
      Bahia, Brazil. _Type_: Museum d'Histoire Naturelle, Paris, no. A
      7669, "skull ... practically perfect" (Thomas, 1921:142).

      _Range._--Island Madre de Deus, Macaco Seco, Andaraí and probably
      islands of the bay of Todos os Santos and valley of the Paraguassú
      River.

      _Diagnosis._--Aristiforms wide; color on setiforms
      Ochraceous-Tawny on upper parts and sides; incisors orthodont;
      molariform teeth with one counterfold, p4 rarely with two.

      _Pelage._--_Aristiforms on middorsal region_: Lanceolate
      aristiforms, with basal part whitish, gradually blackening toward
      tip; total length, 25 to 28 mm; maximum width, 1.2 mm; clavate
      aristiforms with base whitish, gradually blackening toward tip but
      interrupted by Ochraceous-Tawny, subapical zone. _Aristiforms on
      outer thighs_: Whitish on basal half, gradually blackening toward
      tip; total length, 24 to 26 mm; maximum width, 0.9 mm. Some are
      whitish basally, gradually blackening toward distal part but
      distal fourth or fifth near (15'_j_) Ochraceous-Tawny. _Setiforms
      on middorsal region_: Whitish basally, gradually blackening toward
      tip but interrupted by Ochraceous-Tawny, subapical zone; total
      length, 20 to 23 mm; maximum width, 0.1 mm. Some setiforms almost
      completely whitish. _Setiforms on outer thighs_: Whitish basally,
      gradually blackening toward tip but interrupted by near (15'_j_)
      Ochraceous-Tawny, subapical zone; total length, 18 to 20 mm;
      maximum width, 0.06 mm.

      _Skull._--Narrow; bullae small and smooth; jugals dorso-ventrally
      wide with conspicuous transverse ridge; postorbital process of
      zygoma well-developed and formed by jugal and squamosal; posterior
      palatine foramina obsolete; incisive foramen narrow and short;
      vomerine sheath complete or incomplete but premaxillary part at a
      level lower than that of maxillary part (when skull is viewed from
      ventral face); mesopterygoid fossa extending forward as far as
      anterior borders of second molars.

      _Teeth._--Incisors orthodont; molariform teeth with only one
      counterfold, except that p4 rarely has two counterfolds.

      _Comparisons._--From _P. a. sertonius_, _albispinus_ differs in:
      sides of body darker; incisors orthodont as opposed to proodont;
      p4 rarely with two counterfolds instead of always with one
      counterfold.

_Remarks._--The localities where _P. a. albispinus_ has been collected
have a forest climax with a moderate percentage of deciduous trees.

      _Specimens examined._--Total number, 19 (18 CNHM, 1 MCZ), from
      Brazil, Bahia, _Andaraí_, Macaco Seco.


=Proechimys albispinus sertonius= Thomas

      _Proechimys albispinus sertonius_ Thomas, July, 1921, Ann. Mag.
      Nat. Hist., 8 (ser. 9):142 (orig. descr.); Tate, 1935, Bull. Amer.
      Mus. Nat. Hist., 68(5):401; Ellerman, 1940, The families and genera
      of living rodents, Brit. Mus. (Nat. Hist.), 1:122.

      _Type locality._--Lamarão ("about 70 miles north of Bahia City"),
      _Ituiutaba_, Bahia, Brazil; altitude 300 meters. _Type_: British
      Museum (Nat. Hist.), no. 3.9.5.86, adult male; collected on 16
      June, 1903, by Alphonse Robert; original number, 1508.

      _Range._--Known from the type locality and Bonfim; probably
      occupies valleys of Jacuipe and the Itapicurú rivers and littoral
      between them.

      _Diagnosis._--Aristiforms wide; color of setiforms
      Ochraceous-Tawny on back, grading to Ochraceous-Buff on sides;
      incisors proodont; no molariform tooth with more than one
      counterfold.

      _Pelage._--_Aristiforms on middorsal region_: Lanceolate
      aristiforms whitish basally, gradually blackening toward tip;
      total length, 23 to 27 mm; maximum width, 1.3 mm. Clavate
      aristiforms, and some lanceolate ones, whitish basally, gradually
      blackening toward tip but interrupted by Ochraceous-Tawny,
      subapical zone. Some clavate aristiforms without subapical zone
      but blackened in distal part; total length, 23 to 24 mm; maximum
      width, 0.7 mm. _Aristiforms on outer thighs_: Whitish basally,
      gradually blackening toward tip but interrupted by Light
      Ochraceous-Buff, subapical zone; tip slightly darker; some whitish
      basally, grayish in middle and light yellowish toward tip; total
      length, 20 to 22 mm; maximum width, 0.9 mm.
      _Setiforms on middorsal region_: Whitish basal part succeeded by
      grayish, then by long, light, yellowish band, which becomes Light
      Ochraceous-Buff, and blackish tip; total length, 26 to 29 mm;
      maximum width, 0.15 mm. _Setiforms on outer thighs_: Whitish basal
      part succeeded by grayish, then Light Ochraceous-Buff, subapical
      zone and blackish tip; total length, 18 to 20 mm; maximum width,
      0.13 mm.

      _Skull._--Broad; bullae small and smooth; jugals dorso-ventrally
      "wide," with conspicuous transverse ridge; postorbital process of
      zygoma well-developed and formed by both jugal and squamosal;
      incisive foramen narrow and short; vomerine sheath incomplete or
      complete but premaxillary part on a lower level than maxillary
      part (when skull is viewed from ventral face); mesopterygoid fossa
      extending forward as far as anterior faces of second molars.

      _Teeth._--Incisors proodont; molariform teeth with only one
      counterfold.

      _Comparisons._--Differences from _P. a. albispinus_ are given in
      the account of that subspecies.

_Remarks._--Localities where samples were collected are typical
"caatinga" forest, a climax of mainly deciduous trees; cacti are also
common in the region.

      _Specimens examined._--Total number, 10, from Brazil, Bahia, as
      follows: _Ituiutaba_, Lamarão, 4 (1 DZ, 1 CNHM, 1 MCZ, 1 USNM);
      _Bonfim_, Bonfim, 6 (5 DZ, 1 MN).




INCERTA SEDIS


=Proechimys myosuros= (Lichtenstein)

      _Loncheres myosuros_ Lichtenstein, 1818, Das zoologische Museum der
      Universität zu Berlin, (2):18 (_nomen nudum_); Lichtenstein, 1820,
      Abhandl. K. Akad. Wissensch., Berlin (1818-1819):192, pl. 1, fig. 2
      (orig. descr.); Wied, 1826, Beiträge zur Naturgeschichte von
      Brasilien, 2:445.

      _Mus leptosoma_ Brants, 1827, Het geslacht der Muizen door
      Linnaeus opgesteld ..., Berlyn, p. 150; Lichtenstein, 1830,
      Darstellung neuer oder wenig bekannter Säugethiere, Berlin, Heft
      7, pl. 36, fig. and text pages.

      _Mus cinnamoneus_ Lichtenstein, 1830, Darstellung neuer oder wenig
      bekannter Säugethiere, Berlin, Heft 7, pl. 36.

      _Echimys myosuros_ Is. Geoffroy Saint-Hilaire, 1838, Comptes
      Rendus Acad. Sci., 6(26):886, and 1840, Mag. Zool., Paris (ser. 2,
      année 2):15, 33, 53; Allen, 1899, Bull. Amer. Mus. Nat. Hist.,
      12(20):261.

      _Echinomys leptosoma_ Wagner, 1843, Schreber's Säugethiere,
      suppl., 3:341.

      _Echinomys myosuros_ Burmeister, 1854, Syst. ubersicht Thiere
      Brasiliens, p. 199.

      _Proechimys setosus_ Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser.
      9):141.

      _Proechimys myosuros_ Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5):400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _Proechimys leptosoma_ Tate, 1935, Bull. Amer. Mus. Nat. Hist.,
      68(5): 400; Ellerman, 1940, The families and genera of living
      rodents, Brit. Mus. (Nat. Hist.), 1:119.

      _General characters._--Aristiforms wide (1''') and numerous
      on dorsal parts of body; tail longer (9'') than head and body
      (8''); hind feet short (1''6''').

      _Color_ (According to Lichtenstein and Brants'
      descriptions).--Black between ears; dark brown on middorsal line
      with reddish tinge on front and upper side of neck; posteriorly
      from shoulders there is a greasy shine added to color; this dark,
      dorsal band widens posteriorly, there encroaching on sides of
      body; sides lighter brown, sparsely marked with dark brown lines,
      from sides of head caudad to, and including, outer surfaces of
      hind legs; outer sides of forelegs colored like outer sides of
      hind legs; ankles ringed with brown. Tail blackish above, whitish
      below. Upper surfaces of hands and feet white.

      _Skull._--No description of skull or teeth found.

_Remarks._--Thomas (1921:140-143) summarized the available information
on the forms from southeastern Brazil and synonymised _myosuros_ with
_setosus_. The description of _leptosoma_ by Brants applies to this same
species except in a few features. However, neither Brants nor
Lichtenstein described the tail of _myosuros_ as having a white tip or
even as having a heavily pencilled tip, although Wagner (1843:342) in
redescribing Lichtenstein's species indicated that the tail had a white
pencil. He gave also measurements of the head and body, and tail, which
do not agree with the original measurements given by either Lichtenstein
or Brants. Lichtenstein, in the original description, gave the type
locality of _myosuros_ as Bahia, and stated that it was collected by
Freireiss. Brants also gave Bahia as the type locality for _leptosoma_.
The names _leptosoma_ Brants and _cinnamoneus_ Lichtenstein are
evidently no more than duplicate names for _myosuros_, as pointed out by
Thomas (1921:141) and subsequent writers. Specimens referred to any of
these forms, therefore, could take the earlier name _myosuros_ until
identified otherwise. Lichtenstein later (1830, text for plate 36, fig.
2) added São Paulo State to the known range of the species, mentioning
specimens collected there by Sello. Probably, therefore, Wagner
redescribed _leptosoma_ using a composite sample; the white tip on the
tail could occur in any race of _P. iheringi_ from São Paulo.

Considering the short hind feet and the wide aristiforms, _Proechimys
myosuros_ probably will eventually prove to be related to _albispinus_;
perhaps it will prove to be a synonym of _albispinus_.




CONCLUSIONS


      1. The genus _Proechimys_ is divisible into two subgenera. In all
      Brazil there are four full species of each subgenus, or 8 species
      in all. All but one of these are divisible into subspecies of which
      there are 29, making a total of 30 kinds in Brazil; 14 of these are
      here newly named.

      2. It is new information, I think, that: (1) One main fold
      extending entirely across the worn crown of the molariform tooth
      is peculiar to _Trinomys_; in the subgenus _Proechimys_, apparent
      complete division of the crown surface is accomplished by a short
      main fold meeting a counterfold originating on the opposite side
      of the tooth; (2) progressive decrease in size of molariform teeth
      from P4 to M3 is peculiar to the subgenus _Trinomys_; in the
      subgenus _Proechimys_, M2 is largest and the teeth are
      progressively smaller anteriorly.

      3. In the one species, _Proechimys albispinus_, which has the
      widest distribution of aristiforms on the body of any species in
      the genus, some of the aristiforms are clavate. Clavate
      aristiforms occur in the most spiny species of the related genus
      _Echimys_.

      4. In subspecies of any one full species the incisive foramen is
      larger in animals which inhabit arid areas than in those which
      inhabit humid areas. Possibly increased area of moist mucosa
      associated with Jacobson's organ is required in arid areas for
      maintenance of the necessary keenness of smell.

      5. The number of counterfolds in the molariform teeth vary in
      clinal fashion. Their variation is in response to humidity.
      Increasing humidity is correlated with increasing number of folds,
      and decreasing humidity is correlated with decreasing number of
      folds.

      6. Clinal variation correlated with increasing humidity is to be
      seen also in longer tail and darker color of pelage.

      7. The primitive _Proechimys_ probably was large, with a short
      tail, narrow aristiforms, strongly built skull, and five
      counterfolds in each molariform tooth.

      8. Geographic isolation appears to have been a factor in the
      establishment of the two subgenera; the arid belt along the São
      Francisco River and northward to Ceará appears to be uninhabited
      by _Proechimys_ and constitutes a barrier separating the two
      subgenera, _Proechimys_ and _Trinomys_.

      9. This arid belt probably developed relatively early, since in
      deposits of late Pleistocene age, remains of the subgenus
      _Trinomys_ have been found in the area where the subgenus still
      occurs.

      10. The most primitive types occur at the periphery of the range
      of the genus.

      11. Populations from small islands tend to be more primitive than
      populations on the mainland. Insular populations develop a
      homozygous condition with resultant disappearance of secondary
      biotypes.

      12. Insular animals ordinarily are larger than their mainland
      counterpart.




TABLE OF MEASUREMENTS

TABLE 1.--Measurements (in millimeters) of adults of _Proechimys_

  Key:

  A Length of head and body
  B Length of tail
  C Length of hind-foot
  D Length of ear from notch
  E Greatest length of skull
  F Condylo-incisive length
  G Zygomatic breadth
  H Length of nasals
  I Interorbital constriction
  J Palatilar length
  K Crown length of cheekteeth

  ======================================================================================
                         A     B     C     D     E     F     G     H     I     J      K
  --------------------------------------------------------------------------------------
  _P. g. steerei_, [M] [M] Hyutanaham
  USNM 105535           218   123    48    17   53.5  44.0  25.2  19.3  11.7  18.2   8.2
  USNM 105536           217   135    50         55.2  45.3  25.7  20.7  11.4  19.2   8.0
         ?
  USNM 105537                                   56.3  44.9  24.0  20.4  11.4  19.3   8.7
  --------------------------------------------------------------------------------------
  _P. g. goeldii_, [M] Fazenda Paraiso
  AMNH 37489            218          52    20   55.1  44.9  27.0  22.1  12.0  18.6   9.4
         [F]
  AMNH 37488            228   157    49    22   57.3  47.6  27.9  22.1  12.4  20.3   9.6
  ======================================================================================
  _P. s. liminalis_, [M] [M] Rio Quichito
  Mean                  229   145    43    21   58.4  47.6  27.3  21.8  12.9  20.1   8.3
  Maximum               250          45    24   61.7  50.0  28.9  23.0  13.8  21.2   8.8
  Minimum               210          40    18   53.3  44.3  25.5  19.4  12.0  18.5   7.9
  No. of specimens        5     1     5     5    5     5     5     5     5     5     5
         [F] [F]
  MN 6253               215   150    43    20   57.5  46.5  28.3  21.5  12.0  19.4   8.7
  MN 6250               213          42    20   60.8  49.7        22.0  13.7  21.0   9.1
  --------------------------------------------------------------------------------------
  _P. s. amphichoricus_, [M] [M] Esmeralda

  AMNH 77000            252   163    53         60.8  50.3  27.5  24.4  13.7  20.7   9.4
  AMNH 76994            260   160    54                     25.5  22.8  12.6         9.5
  AMNH 77020            250   181    57         62.0  52.0  27.3  25.9  13.8  21.5   9.6
         [F]
  AMNH 76999            235   149    50                           24.0        19.0   9.3
  --------------------------------------------------------------------------------------
  _P. s. kermiti_, [F] Lower Solimões
  AMNH 37124            210          55         65.2  53.7  29.2  27.6  13.5  21.4   9.0
  --------------------------------------------------------------------------------------
  _P. l. brevicauda_, [M] João Pessoa
  DZ 900                245   147    48         58.3  46.6  26.5  22.5  11.6  18.2   8.2
  --------------------------------------------------------------------------------------
  _P. l. boimensis_, [M] Boim
  MCZ 30881             220   160    50         54.6  44.2  24.8  21.0  11.7  17.3   7.5
         [F]
  MN 1976               182   140    45         52.6  42.2  24.3  20.8  11.4  16.8   7.6
         [F] Cametá
  MCZ 30878             240          48         55.1  45.0  25.2  22.4  11.5  18.4   7.6
  --------------------------------------------------------------------------------------
  _P. l. longicaudatus_, [M] Urucum
  CNHM 26732            229   121    48                           21.5  11.5  18.5   8.3
         [F] [F]
  AMNH 37085            210   150    44         51.4  42.5  24.3  19.5  10.8  17.1   8.9
  AMNH 37086            210          50         48.5  40.9  23.7  17.1  10.2  17.1   8.3
  --------------------------------------------------------------------------------------
  _P. l. leucomystax_, [M] Tapirapoã
  AMNH 37509            230   150    43         50.7  42.2  24.5  18.4  10.3  17.5   8.1
         [F]
  AMNH 37510            210          42         48.1  41.3  23.0  16.9   9.9  17.2   8.1
         [F] Utiarití
  MN 2212                                       48.0  39.9        18.3  11.2  15.9   8.0
         [F] Salto Sepotuba
  MN 1936               202   147    44         52.6  43.0  23.6  19.2  10.7  17.8   7.8
  --------------------------------------------------------------------------------------
  _P. l. roberti_, [M] [M] Anapolis
  Mean                  208   159    45    21   52.7  43.5  24.9  20.7  13.1  17.2   7.9
  Maximum               235   190    55    25   56.1  47.8  27.1  23.7  12.0  19.1   8.2
  Minimum               170   135    36    18   48.1  40.0  22.8  18.2  10.6  15.6   7.6
  No. of specimens       16    14    16    16   11    11    11    11    11    11    11
         [F] [F]
  Mean                  219   149    44    20   51.1  42.3  24.1  20.0  10.7  17.2   8.0
  Maximum               290   155    48    24   55.5  45.4  25.8  21.5  11.1  17.7   8.7
  Minimum               195   125    40    18   48.9  40.3  23.1  19.1  10.5  16.6   7.7
  No. of specimens       10     8    10    10    7     7     7     7     7     7     7
  ======================================================================================
  _P. g. villicauda_, [M] [M] Tapirapoã
  MN 1932               225   145    47         55.6  45.5  26.8  24.0  12.0  18.1   8.9
  MN 1934               215   162    50         56.2  46.0  26.1  21.3  12.0  18.6   8.4
         [M] Utiarití
  AMNH 57544            250   200    55                        .  24.3  13.1  19.9   9.1
  --------------------------------------------------------------------------------------
  _P. g. ribeiroi_, [M] Rio 12 de Outubro
  MN 1935               190   134    47         50.1  41.0  24.3  20.0  11.5  15.9   8.1
  --------------------------------------------------------------------------------------
  _P. g. hyleae_, [M] [M] Tauarí
  Mean                  248   146    52         58.1  47.6  27.1  22.9  12.1  19.4   8.5
  Maximum               260   174    53         59.0  47.8     .  23.4  13.2  20.0   8.8
  Minimum               217   143    51         57.2  46.5     .  22.4  11.1  18.8   8.3
  No. of specimens        4     3     4          2     2     1     2     2     2     2
         [F] [F]
  Mean                  229   149    50         54.3  44.9  25.8  21.0  11.8  18.1   8.5
  Maximum               270   168    54         56.1  46.3  27.4  23.0  13.4  19.3   9.0
  Minimum               190   132    49         51.5  42.9  24.5  19.1  11.1  17.1   7.9
  No. of specimens       10     9    10          9    11    11    10    10    10    10
  --------------------------------------------------------------------------------------
  _P. g. nesiotes_, [M] Ilha de Manapirí
  CNHM 19496            201   133    47    20   52.7  42.7  25.1  19.5  11.1  17.8   8.0
         [F]
  MN 1975               200   152    47    21   52.1  42.6  25.8  19.5  12.3  18.3   8.0
  --------------------------------------------------------------------------------------
  _P. g. leioprimna_, [F] [F] Cametá
  AMNH 37484            192   151    41    22   54.8  44.9  25.4  19.2  12.6  18.4   8.4
  CNHM 19503            189   164    47    22   54.4  43.7  26.2  20.5  12.6  18.2   8.2
  CNHM 19536            189          43    22
  --------------------------------------------------------------------------------------
  _P. g. oris_, [M] Providencia
  CNHM 19495            230   170    45    24   56.1  47.1  25.8  22.0  11.4  17.4   8.3
         [M] Tanaquará
  MN 1974               230   175    49    23   53.2  43.0  23.8  20.1  10.5  17.9   7.7
         [M] Rio Guamá
  AMNH 37487            205   142    42    21
  --------------------------------------------------------------------------------------
  _P. g. arescens_, [M] [M] Fazenda Inhuma
  CNHM 26440            206   149    51    24   54.7  44.1  26.3  21.4  12.1  18.7   8.3
  CNHM 26441            191   164    51         55.6  45.0  25.7  22.4  11.7  18.7   8.7
  --------------------------------------------------------------------------------------
  _P. g. riparum_, [F] Manaus
  AMNH 143018           225          44    20   52.6  43.2  24.0  20.5  11.0  17.2   6.7
  --------------------------------------------------------------------------------------
  _P. g. arabupu_, [M] [M] Arabupu
  AMNH 75816            243   220    56         59.2  48.7  27.0  23.8  12.9  17.8   8.7
  AMNH 75819            230   181    52         55.0  46.0  26.0  22.5  12.3  16.9   8.3
  AMNH 75815            228   198    52
         [F] [F]
  AMNH 75810            226   170    48         53.9  45.6  25.6  21.0  12.0  16.1   8.3
  AMNH 75823            209   188    48         53.4  43.9  24.5  21.5  11.7  16.4   8.3
  AMNH 75817            204   167    47         51.1  43.1     .  21.6  11.3  16.6   8.2
  --------------------------------------------------------------------------------------
  _P. dimidiatus_, [M] [M] Pedra Branca
  Mean                  199   170    46         52.4  43.5  26.2  19.5  12.1  16.4   8.3
  Maximum               220   195    50         56.4  47.1  27.5  21.5  13.6  18.0   8.7
  Minimum               180   150    44         48.1  40.4  24.6  17.5  11.0  14.4   7.4
  No. of specimens       19    18    19         45    46    45    45    46    46    46
         [F] [F]
  Mean                  197   162    44         51.8  42.9  25.8  19.4  11.8  16.3   8.3
  Maximum               230   180    46         55.1  45.9  27.4  22.0  13.0  18.4   8.9
  Minimum               165   145    42         48.6  39.5  23.8  17.6  10.7  14.8   7.7
  No. of specimens       14    12    14         42    44    44    42    44    44    44
  --------------------------------------------------------------------------------------
  _P. i. iheringi_, [M] [M] Ilha de São Sebastião
  Mean                  207   197    48         54.5  44.6  26.2  19.9  12.0  18.3   8.3
  Maximum               220   205    50         55.0  45.2  27.1  20.4  12.8  18.7   8.5
  Minimum               196   190    46         53.5  43.7  25.9  19.3  10.9  17.5   8.0
  No. of specimens        5     2     5          5     5     4     4     5     5     5
         [F] [F]
  MN 6453               228   185    46         54.3  44.5  25.9  20.5  11.0  18.9   8.2
  DZ 2095               205   180    46         53.2  42.9  26.4  18.9  11.1  17.0   8.2
  DZ 2525               205          46         56.9  45.8  27.8  20.9  12.5  18.9   8.2
  --------------------------------------------------------------------------------------
  _P. i. bonafidei_, [M] [M] Fazenda Bõa Fé
  Mean                  211   186    50    25   53.3  43.4  25.6  20.2  12.1  16.3   8.5
  Maximum               220   194    54    26   55.8  45.2  26.3  21.7  13.2  17.4   9.1
  Minimum               200   176    47    24   50.7  41.0  24.2  19.1  11.0  14.8   8.1
  No. of specimens        7     5     8     8    4     5     5     7     7     7     7
         [F] [F]
  Mean                  209   185    52    25   52.6  44.4  26.6  20.0  12.4  16.4   8.6
  Maximum               226   203    55    27   56.9  46.4  28.6  21.4  13.2  17.0   9.2
  Minimum               185   153    50    22   44.4  42.3  24.9  18.0  11.4  15.5   8.2
  No. of specimens        7     7     7     7    6     6     7     7     7     7     7
  --------------------------------------------------------------------------------------
  _P. i. gratiosus_, [M] [M] Floresta da Caixa Dagua
  Mean                  193   191    48         51.2  41.4  25.5  18.5  11.7  16.3   8.0
  Maximum               200   200    49         51.7  42.2  27.0  18.9  12.0  16.7   8.2
  Minimum               185   175    47         50.5  40.4  24.6  18.0  11.1  15.6   7.9
  No. of specimens        5     5     5          5     5     5     5     5     5     5
         [F] [F]
  Mean                  204   175    49    24   50.5  42.1  26.0  18.4  11.4  16.3   7.9
  Maximum               220   190    50    26   52.6  43.1  26.6  19.5  12.1  17.5   8.2
  Minimum               195   160    47    22   48.4  41.0  25.3  17.5  10.7  15.3   7.6
  No. of specimens        5     2     5     4    4     4     4     4     4     4     4
  --------------------------------------------------------------------------------------
  _P. i. paratus_, [M] [M] Floresta da Capela de São Braz
  MN 4023               203   195    54    28   51.2  41.7  25.4  18.3  10.4  16.2   8.4
  MN 5458               190   170    51    27
         [F]
  MN 4012               220   210    54    29   52.2  42.3  25.4  19.1  12.3  17.5   8.7
  --------------------------------------------------------------------------------------
  _P. i. panema_, [M] [M] Campinho
  MN 8286               215          45    23   54.0  45.1  27.7  19.5  13.4  16.4   8.1
  MN 8284               195   180    43    23   51.5  41.8  24.5  18.1  11.4  16.0   7.6
         [F] [F]
  MN 8288               190   190    46    21   51.6  42.8  25.3  18.1  11.7  15.7   7.9
  MN 8287               200   190    46    23   52.6  43.6  27.2  18.4  12.5  16.7   8.3
  MN 8285               190          45    24   50.0  41.1  26.6  19.4  12.3  16.1   8.1
  --------------------------------------------------------------------------------------
  _P. i. denigratus_, [M] [M] Mata do Ribeirão da Fortuna
  Mean                  197   218    52    24   51.5  42.2  25.7  18.3  11.3  16.0   8.2
  Maximum               217   242    54    28   55.4  45.3  27.0  20.3  12.4  17.6   8.5
  Minimum               190   204    50    21   48.7  39.5  23.7  16.8  10.4  15.0   8.0
  No. of specimens       10     9     9    10    8     8     8     8     8     8     8
         [F] [F]
  Mean                  201   207    52    24   49.1  41.2  25.0  18.3  11.2  16.0   7.8
  Maximum               225   225    54    28   54.1  44.6  25.7  21.5  11.8  17.1   8.3
  Minimum               180   175    49    20   48.2  39.5  23.5  17.4  10.5  15.5   7.5
  No. of specimens       12    12    12    12    8     8     8     8     8     8     7
  --------------------------------------------------------------------------------------
  _P. s. setosus_, ? No locality
  AMNH 16140                                          39.8  25.2        11.0  15.9   7.6
  --------------------------------------------------------------------------------------
  _P. s. elegans_, [M] Lagoa Santa
  UZM H82               190   190    47    25               24.3  17.5  11.2  16.6   7.7
         ?
  UZM L104                                      48.6  40.8  24.8  16.6  10.3  15.9   7.7
  ======================================================================================
  _P. a. albispinus_, [M] [M] Macaco Seco
  Mean                  175   162    40         45.9  39.7  23.6  15.6  10.6  15.7   7.6
  Maximum               193   173    47         48.2  42.0  24.9  17.1  11.6  17.5   8.2
  Minimum               165   147    38         44.2  38.1  22.7  14.8   9.7  14.3   7.2
  No. of specimens        9     8     9         11    12    12    14    13    14    13
         [F] [F]
  CNHM 20402            187   171    40         46.0  40.8  23.8  14.9  11.3  16.0   7.4
  CNHM 20408                                    47.6  40.7  24.6  17.1  11.2  15.9   8.2
  --------------------------------------------------------------------------------------
  _P. a. sertonius_, [M] Lamarão
  CNHM 18196            190   160    36    25                           11.7
         [M] Bonfim
  MN 6454               185   175    37         45.7  39.8  24.2  15.5  10.7  16.1   7.5
         [F] [F]
  DZ 2636               190   150    35         43.8  37.6  22.8  14.7   9.6  14.5
  DZ 2635               175   155    38         46.7  40.6  23.3  16.9  10.2  15.1   7.4
  --------------------------------------------------------------------------------------




LITERATURE CITED


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  RIBEIRO, ALIPIO DE MIRANDA
      1914. Historia Natural. Zoologia. Mammiferos. Commissão de Linhas
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  THOMAS, OLDFIELD
      1900. Descriptions of new rodents from western South America. Ann.
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  _Transmitted, December 1, 1947._


                                   22-3343




Transcriber's notes:

- inconsistent use of m (for meter/s) throughout the whole book.
  e.g.: 100 m or 120 m, etc.
- 'TABLE 1.--Measurements (in millimeters) of adults of _Proechimys_'
  left in its (remaining) width ( >  col. 75) for best possible overview.