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Title: Comments on the Taxonomy and Geographic Distribution of North American Microtines

Author: E. Raymond Hall
        E. Lendell Cockrum

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Comments on
the Taxonomy and Geographic Distribution
of North American Microtines

BY

E. RAYMOND HALL AND E. LENDELL COCKRUM

University of Kansas Publications
Museum of Natural History
Volume 5, No. 23, pp. 293-312
November 17, 1952

University of Kansas
LAWRENCE
1952

University of Kansas Publications, Museum of Natural History

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

Volume 5, No. 23, pp. 293-312
November 17, 1952

University of Kansas
Lawrence, Kansas

PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS 1952

Comments on
the Taxonomy and Geographic Distribution
of North American Microtines

BY

E. RAYMOND HALL and E. LENDELL COCKRUM

In preparing maps showing the geographic distribution of North American microtines, conflicting statements in the literature and identifications that, if accepted, would result in improbable geographic ranges have led to the examination of pertinent specimens with the results given below. The studies here reported upon were aided by a contract between the Office of Naval Research, Department of the Navy, and the University of Kansas (Nr 161-791), by funds provided by the University of Kansas from its Research Appropriation, and by grants for out-of-state field work from the Kansas University Endowment Association. Grateful acknowledgment is made to persons in charge of the collections at each of the following institutions for permission to use the collections under their charge: Biological Surveys Collection, United States National Museum (herein abbreviated USBS); California Museum of Vertebrate Zoology (MVZ); Chicago Natural History Museum (CNHM); University of Kansas Museum of Natural History (KU); Museum of Comparative Zoology (MCZ); United States National Museum (USNM); Department of Economic Zoology, University of Wisconsin (UWDEZ); and Zoological Museum, University of Wisconsin (UWZM).

When Bole and Moulthrop named Synaptomys cooperi saturatus, with type locality in Illinois, they, in effect, divided the geographic range of Synaptomys cooperi stonei into two parts (see A. B. Howell, N. Amer. Fauna, 50:10 (fig. 2), August 5, 1927) since Bole and Moulthrop (op. cit.) did not assign to any subspecies the specimens from southern Wisconsin that Howell (op. cit.) had identified as S. c. stonei. Bole and Moulthrop's inclusion in their newly named subspecies of a specimen from as far west as East Columbia, Missouri, left in doubt the subspecific identity of specimens from Iowa and a specimen from Arkansas. Howell (op. cit.) had assigned this material from Iowa and Arkansas to S. c. gossii.

Howell recognized that the one individual (168266 USBS) from Lake City, Arkansas, was too young to be identified to subspecies with certainty and assigned the specimen to S. c. gossii "upon geographical grounds" (op. cit.:19). Keith R. Kelson and one of us (Hall) compared this specimen with pertinent materials. As a result of this comparison we refer the specimen, on the same grounds employed by Howell, to Synaptomys cooperi saturatus.

Specimens from approximately the southern half of Wisconsin (from Kelly Lake southward) were referred to S. c. stonei by Howell (op. cit.:16). Now that S. c. saturatus has been recognized, these specimens from southern Wisconsin would be expected to be referable to S. c. saturatus. When these specimens were examined and compared (by Hall and Kelson) with other specimens in the United States National Museum the skulls were found to be much larger than in S. c. cooperi, smaller than in S. c. gossii, and nearly the size of those of Synaptomys cooperi saturatus, to which subspecies we refer the specimens in question.

Howell (op. cit.:16) referred a specimen from Cassopolis, Michigan, a locality that might be presumed to fall within the range of the more recently named S. c. saturatus, to S. c. stonei. Bole and Moulthrop did not mention this specimen when they described and named S. c. saturatus (1942). Neither did Burt, but Cassopolis is within the geographic range ascribed to S. c. cooperi on his map (The Mammals of Michigan, Univ. Michigan Press, p. 213, 1946). Examination (by Kelson and Hall) of the specimen (41777 MCZ) reveals that it resembles S. c. cooperi in shortness of hind foot (18 mm.), shortness of tail (18 mm.), narrowness across zygomata (16 mm.), and grayish pelage. In the long braincase, heavy rostrum, greater condylobasilar length, greater lambdoidal breadth, long rostrum, and longer incisive foramina, it agrees closely with specimens of S. c. saturatus, to which subspecies we refer the specimen.

Necker and Hatfield (Bull. Chicago Acad. Sci., 6:54, 1941) referred specimens from Rosiclaire, Illinois, to S. c. gossii. These specimens were not mentioned by Bole and Moulthrop (op. cit.) when they named S. c. saturatus although the specimens presumably would be referred to the newly-named subspecies. We have examined the pertinent specimens (Nos. 15781-15786 and 16049-16054 CNHM) and find that on the basis of dark color, long and slender skull, heavy incisors, and small cheek-teeth, they are referable to S. c. saturatus Bole and Moulthrop. None, however, has a tail so short as the type of S. c. saturatus. For that matter, the average length of the tail of six near topotypes (5 mi. W, 2½ mi. S Monticello, Piatt County, Illinois, Nos. 32037-32042 KU) exceeds that of the type (17.4 mm., range 12-20, as compared to 14 mm. for the type).

In view of the taxonomic treatment accorded by Bole and Moulthrop (Sci. Publs. Cleveland Mus. Nat. Hist, 5:149-151, September 11, 1942) to the lemming mice of the species Synaptomys cooperi, as explained in the preceding account, it has seemed desirable to examine Iowan specimens of this species. Hall and Kelson examined the necessary material and made the following conclusions. An adult male from Hillsboro (168453 USBS) has the lighter color and large skull of S. c. gossii to which Howell (N. Amer. Fauna, 50:19, August 5, 1927) referred the specimen. The more western specimen from Knoxville, a young male (190358 USNM), is almost exactly the same age as a male of S. c. saturatus from Bascom, Indiana (143701 USNM), and is but slightly older than a male S. c. gossii from Ft. Leavenworth, Kansas (91583 USBS). The upper molariform tooth-row is the same length in the specimens from Kansas and Iowa, but is longer in that from Indiana. The fact that the specimen from Knoxville closely resembles the Kansan specimen in other dimensions of the skull, which is larger than in the specimen from Indiana, gives a basis for applying the name Synaptomys cooperi gossii to the specimen from Knoxville. This is the same name recently used by Fichter and Hansen (Bull. Univ. Nebraska State Mus., 3(2):2, September, 1947) for the Iowan specimens, although they seemingly applied the name without being aware of Bole and Moulthrop's earlier naming of S. c. saturatus (Sci. Publs. Cleveland Mus. Nat. Hist., 5:149, September 11, 1942).

Howell (N. Amer. Fauna, 50:30-31, August 5, 1927) had only eight specimens of this subspecies available when he revised the genus Synaptomys. Of these eight (Maine: Mount Katahdin, 2; New Brunswick: Near Bathurst, 1; New Hampshire: Fabyans, 1, the type; Quebec: St. Rose, 4), only the type and one of the specimens from St. Rose are adults. Concerning the others, Howell wrote (op. cit.:31): "The example from near Bathurst is not adult and has a damaged skull, so is identified provisionally. All other specimens are too young for positive diagnosis."

Since Howell's revision only one additional specimen has been reported. Anderson (Ann. Rept. Provancher Soc. for 1939, p. 71, 1940) reported it from Table Mountain, 3888 ft., Gaspé County, Quebec.

In the collection of the University of Kansas Museum of Natural History there is still another specimen. It is an adult male topotype (No. 6483 KU, formerly No. 72 in the collection of Alfred E. Preble) obtained on August 21, 1905, at Fabyans, New Hampshire. The measurements of this specimen are as follows (measurements in parenthesis are those of the type as given by Howell, op. cit.): Total length, 135 (132); tail, 26 (24); hind foot, 22 (20); condylobasilar length, 25.1 (25.8); rostral length, 6.5 (6.8); rostral breadth, 4.7 (4.9); interorbital breadth, 3.3 (2.8); zygomatic breadth, 15.4 (16.0); lambdoidal breadth, 12.1 (12.4); incisive foramina, 5.9 (5.7); height of skull, 9.1 (9.3).

Howell (op. cit.:30) characterized S. b. sphagnicola as: "Large and high [skull] with narrow interorbital sharply ridged, the ridges of the type being joined for a distance of 4 millimeters; interparietal narrow and rectangular. The rostrum is long, tapering very little, and the nasals, slightly constricted medially are quite narrow posteriorly. The incisive foramina are long and wide." Howell further stated (op. cit.:30-31) that: "It is hard to predict what will be found to constitute the most valuable cranial characters in distinguishing this race from adult medioximus. The discernible differences now are in the shape of the interparietals, rostral characters, and interorbital differences that will probably not hold good when animals of the same age are compared."

As can be seen from a comparison of the measurements given above for the type and the topotype, some of the characteristics given by Howell are not found in the topotype: The interorbital region is not narrow (in fact it is wider than it ordinarily is in some other subspecies of Synaptomys borealis) and the incisive foramina are not longer than in other subspecies of Synaptomys borealis.

As far as present material permits us to judge, Synaptomys borealis sphagnicola is characterized, cranially, by: Skull large; interorbital region sharply ridged (the ridges being joined for a distance of 4 mm. in the type and of 4.5 mm. in the topotype); rostrum long, tapering relatively little; nasals slightly constricted medially and unusually narrow posteriorly; interparietal narrow and rectangular.

Prior to 1935 caurinus was considered to be a monotypic species. In 1935 Racey and Cowan (Rept. British Columbia Provincial Museum for 1935, pp. H 25-H 26) examined material from southwestern British Columbia of C. caurinus, including a series of 24 specimens from Alta Lake, and compared it with Clethrionomys gapperi occidentalis and C. g. saturatus. They found caurinus to be distinct from C. g. saturatus but were "not convinced that occidentalis and caurinus both merit systematic recognition; should they prove to be indistinguishable, as the little available material indicates, occidentalis will take precedence on grounds of priority. It is our opinion that further study of the distribution of the genus in British Columbia will lead to the recognition of occidentalis as the form inhabiting coast-line and saturatus the interior of British Columbia" p. H 26. In the face of these opinions Racey and Cowan nevertheless recognized caurinus under the name Clethrionomys gapperi caurinus (Bailey).

In spite of the treatment by Racey and Cowan (op. cit.) of occidentalis and caurinus as subspecies of C. gapperi, later authors arranged occidentalis as a member of the "californicus" group although they retained caurinus in the gapperi group. For example, Davis (The Recent Mammals of Idaho, The Caxton Printers, pp. 307-308, 1939) assigned C. caurinus to the gapperi group, although he regarded C. caurinus as a species (not a subspecies). He regarded also C. occidentalis as a species (not a subspecies) but assigned it to the californicus group. Dalquest (Univ. Kansas Publ., Mus. Nat. Hist., 2:344, April 9, 1948) considered occidentalis to be conspecific with Clethrionomys californicus and wrote (op. cit.:101): "The californicus group, I feel, contains only the races of Clethrionomys californicus, while the gapperi group contains C. gapperi and its races, including caurinus, and possible other species." Dalquest gave no indication that he had examined any specimens of caurinus.

When Dalquest (op. cit.:344) arranged occidentalis and californicus as subspecies of the same species, he used the name combination Clethrionomys californicus occidentalis because he ignored, or was unaware of, the page priority of occidentalis over californicus. We regard the anterior position of occidentalis as nomenclatural priority and therefore employ occidentalis rather than californicus as the specific name.

Differences between the gapperi group and the occidentalis group include: postpalatal bridge (complete in both groups) truncate posteriorly in the gapperi group and with a median, posteriorly directed, spine in the occidentalis group (this character is not evident in all specimens; some gapperi have a spine, and some occidentalis have the spine much reduced); dentition of the occidentalis group is heavier; enamel pattern of M3 and m1 in occidentalis more simplified—the number of salient and re-entrant angles tends to be reduced in adults of the occidentalis group.

An examination of specimens of caurinus (British Columbia: Mt. Seymour, 2 KU; Lund, Malaspina Inlet, 2 USBS; and Inverness, mouth Skeena River, 1 USBS), reveals that, in the presence of the median postpalatal spine and in the characters of the molars, caurinus agrees with the occidentalis group.

The red-backed mouse of the Olympic Peninsula was originally accorded specific rank. Currently it stands in the literature as a subspecies of the wide-spread species Clethrionomys gapperi because Dalquest (Univ. Kansas Publ. Mus. Nat. Hist., 2:343, April 9, 1948) used the name-combination Clethrionomys gapperi nivarius. Taylor and Shaw had earlier (Occas. Papers Charles R. Conner Mus., 2:23, 1929) indicated the same status by using the name Evotomys gapperi nivarius. Davis (The Recent Mammals of Idaho, The Caxton Printers, Caldwell, Idaho, p. 306, April 5, 1939), however, indicated that the affinities of nivarius were with the californicus [= occidentalis] group, although he treated nivarius as a distinct species. We have examined two adult females (K. U. Nos. 10707 and 10708) of nivarius from Reflection Lake, 3800 ft., Jefferson County, Washington, and on the basis of their thick, instead of thin, pterygoid processes concur with Davis that the affinities of nivarius are with the named kinds of Clethrionomys now arranged as subspecies of Clethrionomys occidentalis, rather than with the kinds now arranged as subspecies of Clethrionomys gapperi. Although we are aware that Dalquest (op. cit.:101-102) did not find actual intergradation between nivarius and Clethrionomys occidentalis occidentalis—a ten-mile gap separated their ranges—we prefer to use the name combination Clethrionomys occidentalis nivarius. In doing so we recognize that intergradation ultimately may be found between the two species C. occidentalis and C. gapperi; in that event the name gapperi will apply as the name of the species because it has priority over occidentalis.

The following named kinds of Clethrionomys are considered to be subspecies of Clethrionomys occidentalis:

Clethrionomys occidentals occidentalis (Merriam).

Clethrionomys occidentalis californicus (Merriam).

Clethrionomys occidentalis caurinus (Bailey).

Clethrionomys occidentalis mazama (Merriam).

Clethrionomys occidentalis nivarius (Bailey).

Clethrionomys occidentalis obscurus (Merriam).

The name rufescens, as applied by R. W. Smith (Amer. Midland Nat., 24:233, July, 1940) to the red-backed mouse of Nova Scotia, seems to be unavailable under the rules of the International Code of Zoological Nomenclature, since it is a homonym of Arvicola rufescens de Selys Longchamps, 1836, which in turn is a synonym of Clethrionomys glareolus glareolus Schreber, 1780 (Ellerman and Morrison-Scott, Checklist of Palaearctic and Indian Mammals, 1758 to 1946, p. 663, November 19, 1951).

When Swarth (loc. cit.) named the red-backed mouse of the mainland of southern Alaska as a new subspecies, he characterized it as "Size rather large. Differs from E. [= Clethrionomys] wrangeli, nearest it geographically, in cranial characters and in much longer tail; from E. caurinus, the species to the southward in British Columbia, in larger size and longer tail." He remarked (loc. cit.): "I had supposed that the red-backed mouse occurring on the mainland coast of this region would prove to be E. wrangeli, but the latter appears to be purely an insular species. I have had no specimens of that race for comparison, but the Evotomys secured differ so widely from it in all the essential peculiarities of the species as given in the published descriptions that there seems little doubt of their belonging to a different species. Wrangeli has a short tail, less than twice as long as the hind foot—in adults of phaeus the tail is invariably more than twice the length of the foot, frequently more than a third of the entire length of the animal."

The external and cranial measurements of two subadults in the United States National Museum (No. 217413 from Quadra Lake and No. 217415 from Marten Arm, Boca de Quadra, taken in mid-February) and three old adults from Fort [= Port] Simpson, British Columbia (Nos. 90263-90264, 90272 USBS), are almost the same as those given by Swarth in the original description of Clethrionomys phaeus.

In cranial measurements, as well as in the structure of the palate and last upper molar, C. phaeus agrees with the gapperi group (to which it has been assigned by Davis, The Recent Mammals of Idaho, The Caxton Printers, p. 306, April 5, 1939, and by Orr, Jour. Mamm., 26:69, February 12, 1945) and differs from Clethrionomys occidentalis caurinus (which was assigned above to the occidentalis group, formerly the californicus group).

Since the measurements of specimens examined by us, as well as those recorded by Swarth (op. cit.), fall within the range of those of the species Clethrionomys gapperi, and since the differences between phaeus and C. g. saturatus are of the kind and degree that separate subspecies in C. gapperi we employ the name combination Clethrionomys gapperi phaeus (Swarth). C. g. saturatus, as understood by us, occurs to the southeast of C. g. phaeus in the Rocky Mountains of British Columbia, and in northeastern Washington, northern Idaho and northwestern Montana.

Specimens examined.—Total, 23, distributed as follows: Alaska: Chickamin River (Behm Canal), 15 (MVZ); Boca de Quadra, 3 (MVZ); Marten Arm, Boca de Quadra, 1 (USNM); Quadra Lake, 1 (USNM). British Columbia: Fort [= Port] Simpson, 3 (USBS).

When Bailey (loc. cit.) named the red-backed mouse from Wrangell Island, Alaska, he characterized it as "A large, dull-colored species entirely distinct from any known form," and remarked: "In no way does E. [= Clethrionomys] wrangeli show a close relationship to any other American species. In size and relative proportions it comes closest to E. dawsoni, from which it differs widely in coloration and more widely in cranial characters. With the long-tailed species south and east of its range there is no need of comparison."

Swarth (Univ. California Publ. Zool., 24:173, June 17, 1922) reported that three specimens from Flood Glacier and 23 from Great Glacier, British Columbia, and four from Sergief Island, at the mouth of the Stikine River, Alaska, were: "All E. wrangeli, indistinguishable from specimens at hand from Wrangell Island." Swarth further reported that, although he found no intergradation between Clethrionomys wrangeli from Flood Glacier and the nearly adjacent Clethrionomys rutilus dawsoni, "the two species, however, resemble each other so closely in form, and in some pelages in color also, that wrangeli would seem to be a coastal offshoot of dawsoni...."

Davis (The Recent Mammals of Idaho, The Caxton Printers, p. 306, April 5, 1939) and Orr (Jour. Mamm., 26:69, February 12, 1945) more recently have shown that Clethrionomys wrangeli is not a member of the rutilus group (to which C. dawsoni belongs) but is a member of the gapperi group.

Our comparisons of a series of eight topotypes of wrangeli (all in the Biological Surveys Collection) with several subspecies of Clethrionomys gapperi (including phaeus, saturatus, galei, brevicaudus, and others) reveal that the differences seen in wrangeli are of the kind and degree that serve to separate subspecies. The red-backed mouse from Wrangell Island, then, should stand as Clethrionomys gapperi wrangeli (Bailey).

Specimens examined.—Total, 31, distributed as follows: Alaska: Wrangell, Wrangell Island, 27 (19 MVZ., 8 USBS); Sergief Island at mouth of Stikine River, 4 (MVZ).

Table 1. External and cranial measurements of Clethrionomys.

^*Superior numbers denote the number of individuals averaged.

Measurements.—External and cranial measurements of adults are given in table 1.

Remarks.—Morphologically C. g. stikinensis shows greater resemblance to C. g. solus of Revillagigedo Island, than to the geographically adjacent subspecies C. g. wrangeli and C. g. phaeus. Possibly the original stock of C. g. solus was rafted to Revillagigedo Island from the Cleveland Peninsula.

Hanson (Trans. Wisconsin Acad. Sci., Arts, and Letters, 36:124, 1944) reported two pine mice from near Prairie du Sac, in Westpoint Township, Columbia County, Wisconsin, as Pitymys pinetorum scalopsoides but cast doubt upon their subspecific identity. He also reported pine mice from Blue Mounds, Dane County, Wisconsin. We have examined these specimens (Westpoint, Columbia County, 2—No. 544, skin only, UWDEZ, and No. 521, skin only, H. C. Hanson's private collection; Westpoint, Dane County, 1, No. 11620, UWZM; Vermont, Dane County, 2, Nos. 11674 and 11694, UWZM) and have compared them with topotypes of P. p. schmidti, and with specimens of P. p. nemoralis and P. p. scalopsoides. The specimens from Columbia and Dane counties differ from P. p. schmidti in the greater zygomatic breadth, and lesser height of skull. They differ from P. p. nemoralis of comparable age in shorter tooth-row and generally smaller skull. The interorbital region, however, is wider. In all of the features mentioned above, the specimens in question agree with Pitymys pinetorum scalopsoides, to which subspecies they are here referred.

Allen (loc. cit.) described this species on the basis of two specimens from Aztec, New Mexico, and three from La Plata, New Mexico. He characterized it as "Size large; pelage very full and soft; tail short; skull very narrow.

"Above grayish brown with a tinge of pale buff; fur blackish plumbeous beneath the surface, tipped with pale yellowish brown, and varied with longer, projecting, black-tipped hairs; below grayish white, the fur plumbeous beneath the surface and tipped with white, giving a whitish gray effect. Feet dusky; tail dusky brown above, dull white below."

Allen identified as this species "a large Arvicola from Estes Park, Colorado, which I have before been unable to allocate. I am unable to find that it differs in any particular from the specimens from New Mexico." He pointed out also (op. cit.:73-74) that "The type and only positively identified specimen of Baird's Arvicola modesta [= Microtus pennsylvanicus modestus (Baird)] from Sawatche Pass, Colorado, is a very young specimen in poor condition. An examination of a series of adult and young examples from the type locality will be necessary in order to determine its relationships to A. alticolus [= Microtus longicaudus alticolus (Merriam)] and A. aztecus."

Bailey, in his revision of the American voles of the genus Microtus (N. Amer. Fauna, 17:20), showed Arvicola modesta Baird to be a subspecies of Microtus pennsylvanicus but retained Microtus aztecus (Allen) as a distinct species. In describing M. aztecus he wrote "the size similar to M. pennsylvanicus, but with shorter tail and larger hindfoot; skull long; braincase narrow; interparietal long ..." and remarked that "Microtus aztecus belongs to the pennsylvanicus group. Externally it is not very different from modestus, but none of the specimens show any signs of intergradation; and the skull characters are so well marked that there seems no doubt of its full specific rank."

Subsequent to the publication of Allen's (op. cit.) account and Bailey's account (op. cit.), additional material was collected that helps to clarify the relationships of Microtus aztecus. A comparison of six adult topotypes of Microtus aztecus with a series of nine adults of M. p. modestus from 1 mi. S, 2 mi. E Eagle Nest, 8100 ft., Colfax County, New Mexico, with three adults from 1½ mi. E Manassa, Conejos County, Colorado, and with four adults from Saguache County, Colorado (all in KU), reveals that the supposed "well marked" external and cranial differences between the two forms are not nearly so evident as was indicated by Bailey.

The cranial differences that exist between these two forms (narrower nasals, slightly longer interparietal, slightly longer and narrower skull in aztecus) are evident only as averages. Although geographically intermediate specimens are lacking, the morphological differences between the two kinds of animals are of the degree and kind that separate subspecies, rather than species. We therefore judge M. aztecus (Allen) to be only subspecifically distinct from M. pennsylvanicus modestus and employ the name Microtus pennsylvanicus aztecus.

Taylor and Shaw (Occas. Papers Charles R. Conner Mus., State College Washington, 2:24, December, 1929) list under Microtus nanus [= montanus] canescens material from Calispell Peak, Washington. Probably the basis for this record is a specimen in the Biological Surveys collection (adult male, 236474) taken on May 9, 1921, by G. G. Cantwell, and labelled as Calispell Peak, 9 mi. W Locke, 3500 ft., Pend Oreille County. An examination (by Hall and Kelson) of the specimen discloses that it is of the species Microtus pennsylvanicus, and that it falls within the geographic range ascribed to the subspecies Microtus pennsylvanicus funebris by Dalquest (Univ. Kansas Publ., Mus. Nat. Hist., 2:346, April 9, 1948).

When Murie (Jour. Mamm., 11:75, February 11, 1930) named the meadow mouse from Amak Island, Alaska, as amakensis, he arranged it as a separate species. One of us (Hall) and K. R. Kelson examined the type and topotypes of amakensis in the Biological Surveys collection in the U. S. National Museum and compared them with series of Microtus oeconomus operarius, M. o. sitkensis, M. o. elymocetes, M. o. yakutatensis, and M. o. kadiacensis. Among the specimens examined of the latter subspecies were 17 from Izambek Bay, Kodiak Peninsula, on the mainland opposite Amak Island, the type locality of amakensis. The characters given by Murie (op. cit.) serve to separate amakensis from closely related neighboring kinds of meadow mice, but are of the degree and kind that, in this group of meadow mice, separate subspecies rather than species. Although actual intergrades are lacking, the animals from Amak Island are considered to be only subspecifically distinct and to belong to the oeconomus complex. The name Microtus oeconomus amakensis is applied to them.

Dalquest (Univ. Kansas Publ., Mus. Nat. Hist., 2:353, April 9, 1948) assigned all the meadow mice of the species Microtus longicaudus from approximately the eastern half of Washington State to Microtus longicaudus halli Hayman and Holt and, in doing so, excluded the subspecies Microtus longicaudus mordax from that state. This assignment of specimens in Washington had the effect of separating the geographic range of M. l. mordax into two parts. One part was in south-central British Columbia and the other part was mainly in the Rocky Mountain region of the United States. Hall and Kelson examined specimens in the Biological Surveys collection in the U. S. National Museum in an attempt to determine more precisely the ranges of the subspecies in southern Canada, Washington, and Idaho.

Microtus longicaudus angustus [= M. l. halli] was described by one of us (Hall, Univ. California Publ. Zool., 37:13, April 10, 1931) as differing from mordax in narrower braincase, higher skull near the anterior end of the frontals, darker coloration, and seemingly smaller size. After examining the material in the U. S. National Museum no reason is seen at the present time to amend this characterization, except to add that some specimens of M. l. mordax are as dark as seasonably comparable specimens of M. l. halli.

Examination of specimens of Microtus longicaudus from Washington east of the Cascade Range (those from the Blue Mountain area excepted) discloses that the skulls do not differ essentially from those of topotypes of M. l. mordax, but do differ, as outlined above, from near-topotypes of M. l. halli. There is considerable variation in color among the Washington-taken specimens of Microtus longicaudus. Animals from the eastern flanks of the Cascades average darker than those taken, north of the Snake River, still farther east in Washington. Possibly Dalquest (op. cit.) relied mainly upon this darker color in assigning the specimens from eastern Washington to M. l. halli. Relying principally upon cranial characters, we conclude that most of the specimens are better referred to M. l. mordax and that M. l. halli is restricted, in Washington, to the Blue Mountains.

Specimens examined of Microtus longicaudus mordax.—Total, 74, all in the Biological Surveys Collection, distributed as follows: Washington: Okanogan County: mouth of Holmar Creek, W Fork Paysaten River, 4700 ft., 1; Conconully, 3; Twisp, 1; Omak Lake, 1200 ft., 3. Stevens County: 5 mi. N Colville, 1. Pend Oreille County: 9 mi. N Metalina, 2600 ft., 1; Sullivan Lake, 3000 ft., 3. Chelan County: Sethekin, 1079 ft., 3; head of Lake Chelan, 900 ft., 12; Hart Lake, Railroad Creek, 3900 ft., 1; Entiat, 20 mi from mouth of Entiat River, 1680 ft., 13; Wenatchee, 4. Douglas County: Waterville, 1. Jefferson County: Cleveland, 2. Kittitas County: 2 mi. S Blewett Pass, 3000 ft., 6: Ellensburg, 1500 ft., 4. Whitman County: Colfax, 2. Yakima County: McAllister Meadows, Tieton River, 3000 ft., 3; Gotchen Cr., 5500 ft., near Sava Spring, Mt. Adams, 2. Klickitat County: 8 mi. S Glenwood, base Mt. Adams, 2. Asotin County: Anatone, 3300 ft., 4; Bly, 1000 ft., 2.

Rausch (Jour. Washington Acad. Sci., 40:135, April 21, 1950) proposed the name Microtus miurus paneaki, with type locality at Tolugak Lake (lat. 68° 24′ N, long. 152° 10′ W), Brooks Range, Alaska, for a meadow mouse of the subgenus Stenocranius. This place is only approximately forty miles east and north of the type locality of the earlier named Microtus muriei, also a member of the subgenus Stenocranius. Large series of specimens of this subgenus, from the Arctic Slope of Alaska, are in the Museum of Natural History of the University of Kansas. Study of these indicates that the differences, which Rausch (op. cit.:136) described as distinguishing his M. m. paneaki from M. muriei, result from differences in age of the specimens, and possibly in part from differences in seasonal condition of pelage. For example, Rausch thought that M. m. paneaki was larger than M. muriei but our specimens reveal that such is not the case. The measurements given below of the type specimen of M. muriei (after Nelson, original description) and measurements (in parentheses) of an immature female (43807 K. U.) of Microtus miurus muriei from Chandler Lake, 68° 12′, 152° 45′, 2900 ft., Alaska, show close correspondence in size. Total length, 119 (122); tail vertebrae, 24 (24); hind foot, 20 (20); condylobasal length, 24.3 (24.5); zygomatic breadth, 10.7 (11.0); greatest width of braincase, 9.0 (9.0); length of nasals, 6.5 (6.0); basal width of rostrum, 4.0 (4.3). In the light of all of the evidence now available, it seems best to treat Microtus miurus paneaki Rausch as a synonym of Microtus muriei Nelson.

Quay (Jour. Mamm., 32:95, February 15, 1951) identified fifty-eight specimens from the Seward Peninsula of Alaska as Microtus miurus oreas Osgood. Through the courtesy of Dr. Charles P. Lyman, fifteen of Quay's specimens in the Museum of Comparative Zoology at Harvard College have been examined by one of us (Hall). These specimens are as follows: Lava Lake (43378, 43379, 43381, 43382, 43386, 43467 and 43478); Mt. Boyan (43384, 43385, 43463 and 43477); Anvil Hill [= Peak], Cooper Gulch (43377, 43464 and 43473); ——? Lake, 43383. Although we are not prepared to say that these specimens are M. m. muriei, they seem to resemble M. m. muriei as closely as they do any other named form and we here refer them to that subspecies.

The facts are that a critical taxonomic study of the American specimens of the subgenus Stenocranius is required in order to ascertain the geographic variation. One of us (Hall) has examined the holotypes of the kinds named from Alaska, and the material listed by R. Baker (Univ. Kansas Publ. Mus. Nat. Hist., 5:109) of the two kinds named from Canada. The degree and nature of the variation shown by these specimens lead us to the conclusion that all are of a single species. If the American mouse is specifically distinct from any of the previously named Asiatic species—at this writing we lack material to decide this question—the named kinds from the mainland of the New World may stand as follows:

Microtus miurus andersoni Rand.

Microtus miurus cantator Anderson.

Microtus miurus miurus Osgood.

Microtus miurus muriei Nelson.

Microtus miurus oreas Osgood.

Transmitted July 8, 1952.

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