The Project Gutenberg EBook of Geographic Variation in Red-backed Mice (Genus Clethrionomys) of the Southern Rocky Mountain Region, by E. Lendell Cockrum and Kenneth L. Fitch This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org Title: Geographic Variation in Red-backed Mice (Genus Clethrionomys) of the Southern Rocky Mountain Region Author: E. Lendell Cockrum Kenneth L. Fitch Release Date: June 4, 2010 [EBook #32679] Language: English Character set encoding: ASCII *** START OF THIS PROJECT GUTENBERG EBOOK RED-BACKED MICE *** Produced by Chris Curnow, Tom Cos, Joseph Cooper and the Online Distributed Proofreading Team at http://www.pgdp.net Geographic Variation in Red-backed Mice (Genus Clethrionomys) of the Southern Rocky Mountain Region BY E. LENDELL COCKRUM and KENNETH L. FITCH University of Kansas Publications Museum of Natural History Volume 5, No. 22, pp. 281-292, 1 figure in text November 15, 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. 22, pp. 281-292, 1 figure in text November 15, 1952 ~University of Kansas~ Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1952 [Illustration: Union Label] 24-4369 Geographic Variation in Red-backed Mice (Genus Clethrionomys) of the Southern Rocky Mountain Region BY E. LENDELL COCKRUM and KENNETH L. FITCH In the course of the preparation of a synopsis of the North American terrestrial microtines by one of us (Cockrum), and the completion of a Master's thesis on the geographical variation of the red-backed mice of Wyoming by the other (Fitch) we had occasion to study the red-backed mice of the southern Rocky Mountain region (see figure 1). Results of these studies are the recognition of two heretofore unnamed subspecies of the red-backed mouse in the southern Rocky Mountain region, and a clarification of the taxonomic status of two additional kinds. +Clethrionomys gapperi galei+ (Merriam) 1890. _Evotomys galei_ Merriam, N. Amer. Fauna, 4:23, October 8. 1931. _Clethrionomys gapperi galei_, Hall, Univ. California Publ. Zool., 37:6, April 10. 1897. _Evotomys gapperi galei_, Bailey, Proc. Biol. Soc. Washington, 11:126, May 13. _Type locality._--Ward, 9500 feet, Boulder County, Colorado. _Range._--The Rocky Mountains of extreme southern Alberta, Montana, northwestern and southern Wyoming, and north and central Colorado. _Remarks._--_C. g. galei_, with the largest geographic range of any of the Rocky Mountain subspecies, is also the most variable. Three principal areas of geographic variation were found. These areas are: The mountains of north-central Colorado and southern Wyoming (this area includes the type locality); the Big Horn area probably northwest into Montana (no adult specimens from Montana or Alberta examined); and the Teton area which includes the mountains east and southeast of Yellowstone National Park. Specimens from these areas have noticeable differences in pelage, but no constant cranial differentiation could be detected. Specimens from the Medicine Bow Mountains of southern Wyoming have a more reddish dorsal stripe, and more buff and less gray on the sides than either of the northern geographic variants. The dorsal stripe continues farther anteriorly and is better defined through its entire length. There are fewer differences between the two northern geographic variants than between either one of them and the southern variant. Specimens from the Teton Mountains, however, have grayer sides, and the outer margin of the ear is tipped with chestnut (little or no chestnut shows on the ears of the specimens from the Big Horn Mountains); the dorsal stripe is less distinct (with slightly more gray throughout) than in either of the other geographic variants of the one subspecies. Three specimens (two adults) are available from the Little Medicine Range in Converse County (22 miles south and 24.5 miles west of Douglas, 7600 feet), Wyoming. Although red-backed mice probably are found in the mountains of Natrona and Albany counties, the population, in the Little Medicine Range is somewhat isolated. In coloration these mice are lighter than any of the three geographic variants described above; the dorsal stripe is narrower; the sides are more buffy; the dorsal stripe does not project anteriorly beyond the ears as it does in the specimens from the Medicine Bow Mountains; and the face is grayer. These specimens resemble the population in the Big Horn Mountains to the north more than the population in the Medicine Bow Mountains. The specimens from the Little Medicine Range, the Big Horn Range, and the Tetons are possibly subspecifically distinct from the southern specimens. Examination of specimens now allocated to _galei_ from Montana and Alberta should aid in revealing whether the northern animals are an unnamed subspecies. _Specimens examined._--Total, 167, distributed as follows and unless otherwise stated, in the collection of the University of Kansas Museum of Natural History: +Wyoming+: _Park County_: 28 mi. N and 3 mi. W Cody, 7200 ft., 1. _Big Horn County_: Medicine Wheel Ranch, 28 mi. E Lovell, 9000 ft., 22; 17-1/2 mi. E and 4-1/2 mi. S Shell, 1. _Teton County_: Moran, 6244 ft., 4; Moran, 3 (James Findley Collection); 2-3/4 mi. E Moran, 6300 ft., 1; 3-3/4 mi. E and 1 mi. S Moran, 6200 ft., 10. _Washakie County_: 9 mi. E and 9 mi. N Tensleep, 8200 ft., 3; 9 mi. E and 4 mi. N Tensleep, 7000 ft., 1. _Johnson County_: 4 mi. W and 1 mi. S Klondike, 6500 ft., 1; 6-1/2 mi. W and 2 mi. S Buffalo, 5620 ft., 1. _Lincoln County_: 3 mi. N and 11 mi. E Alpine, 5650 ft., 1. _Sublette County_: 31 mi. N Pinedale, 8025 ft., 1. _Fremont County_: Togwotee Pass, 5 (James Findley Collection); 20-1/2 mi. W and 2 mi. S Lander, 1; Mocassin [=Moccasin] Lake, 19 mi. W and 4 mi. N Lander, 10,100 ft., 3; 18 mi. W and 3 mi. N Lander, 1; Mosquito Park Ranger Station, 17-1/2 mi. W and 2-1/2 mi. N Lander, 9500 ft., 10; 6-1/2 mi. W and 17 mi. S Lander, 8450 ft., 4; 5-1/2 mi. W and 22 mi. S Lander, 8800 ft., 3. _Converse County_: 22 mi. S and 24-1/2 mi. W Douglas, 7600 ft., 3. _Carbon County_: 18 mi. SW Rawlins, 7500 ft., 2; 19 mi. E and 8 mi. N Encampment, 9150 ft., 4; 19-1/2 mi. E and 6 mi. N Savery, 8800 ft., 1; 11 mi. E and 6 mi. N Savery, 8400 ft., 1; 14 mi. E and 6 mi. N Savery, 1. _Albany County_: 3 mi. ESE Browns Peak, 10,000 ft., 59. +Colorado+: _Rio Blanco County_: 9-1/2 mi. SW Pagoda Peak, 7700 ft., 2. _Boulder County_: 2-1/2 mi. S Estes Park, 8400 ft., 2; 3 mi. S Ward, 8. _Clear Creek County_: 2 mi. S Idaho Springs, 8000 ft., 1. _Gunnison County_: Gothic, 8 mi. N Crested Butte, 6 (James Findley Collection). _Additional records._--+Colorado+: _Rio Blanco Co._: 25 mi. NE Meeker (Cary, N. Amer. Fauna, 33:120, 1911). _El Paso Co._: Lake Moraine, 10,250 ft. (Warren, Mammals of Colorado, p. 224, 1942). [Illustration: Map Geographic Range Clethrionomys gapperi] ~Fig. 1.~--Geographic ranges of the subspecies of _Clethrionomys gapperi_ in the southern Rocky Mountains. [Map Numbers For shaded areas.] 1. _C. g. galei_ 3. _C. g. uintaensis_ 5. _C. g. limitis_ 2. _C. g. brevicaudus_ 4. _C. g. gauti_ 6. _C. g. arizonensis_ +Clethrionomys gapperi brevicaudus+ (Merriam) 1891. _Evotomys gapperi brevicaudus_ Merriam, N. Amer. Fauna, 5:119, July 30. 1897. _Evotomys brevicaudus_, Bailey, Proc. Biol. Soc. Washington, 11:129, May 13. 1942. _Clethrionomys gapperi brevicaudus_, Bole and Moulthrop, Sci. Publ. Cleveland Mus. Nat. Hist., 5:153, September 11. _Type locality._--Three miles N Custer, 6000 ft., South Dakota. _Range._--The Black Hills of South Dakota and Wyoming. _Remarks._--Merriam (N. Amer. Fauna, 5:119, July 30, 1891) named this subspecies on the basis of two specimens collected in the Black Hills of South Dakota in July, 1888, and assigned it to the species _Evotomys_ [= _Clethrionomys_] _gapperi_. He reported the diagnostic characteristics as: "Similar to _E. gapperi_, but with larger ears and shorter tail. The hazel of the dorsal area is not so bright as in _gapperi_; the sides are the same golden brown." Of the cranial and dental characteristics he wrote: "Much as in _E. gapperi_." Bailey (Proc. Biol. Soc. Washington, 11:129, May 13, 1897), in his "Revision of the American voles of the genus _Evotomys_," with one additional specimen available, raised the Black Hills population to specific status, re-emphasizing the shortness of the tail, and pointing out a few slight cranial differences ("zygomatic arches low and flaring out, so that the inner instead of the outer side shows in top view; auditory bullae as large as in _gapperi_, but less rounded"). Bailey (_loc. cit._) remarked that: "though based on so scanty material, the characters distinguishing the species are fairly pronounced. Its range is isolated and widely separated from that of any other members of the genus by open prairie country and a wide belt of the Transition zone. There seems to be no valid reason for considering it a subspecies." Additional specimens have been taken in recent years from the Black Hills of South Dakota and northeastern Wyoming. This material has shed light on the relationships and morphological characteristics of the red-backed mice of this region. Bole and Moulthrop (Sci. Publ. Cleveland Mus. Nat. Hist., 5:153, September 11, 1942) listed, as comparative material, eight specimens from Bull Springs, Custer County, South Dakota, under the name _Clethrionomys gapperi brevicaudus_ (Merriam). They gave no reason for arranging _brevicaudus_ as a subspecies of _C. gapperi_. Twenty adults (11 skins and skulls, 9 skulls only) from Pennington County, South Dakota (specimens in the University of Michigan Museum of Zoology), have the following measurements (averages of external measurements based on 11 specimens only): Total length, 142 (123-155); tail, 35 (30-39); hind foot, 19.5 (18.6-21.0); basal length, 23.3 (21.7-24.5); condylobasilar length, 23.3 (21.9-24.5); zygomatic breadth, 13.7 (12.9-14.7); lambdoidal breadth, 11.7 (11.3-12.9); alveolar length upper cheek-teeth, 5.5 (5.2-5.8); interorbital breadth, 3.9 (3.6-4.1); length of nasals, 7.7 (7.1-8.5); breadth of rostrum, 3.2 (2.9-3.6); and length of incisive foramina, 5.0 (4.6-5.3). Measurements of the type and one "more fully adult topotype" (as given by Bailey, _op. cit._) are: Total length, 125, 130; tail length, 31, 32; hind foot, 19, 19; basal length, 21.2, 21.8; length of nasals, 6.6, 7.0; zygomatic breadth, 12.5, 12.8; mastoid breadth, 11.3, 11.0; alveolar length of upper molar series, 5.4, 5.3. In every measurement the figures for Bailey's specimens are smaller than the average of the same measurement in the 20 adults from Pennington County, and, in most measurements, are even lower than the minimum of the latter series. Therefore, we conclude that the material available to Merriam (_op. cit._) and Bailey (_op. cit._) consisted of only subadults. In comparison with a series of 23 adult _Clethrionomys gapperi galei_ from 28 mi. E Lovell, Big Horn County, Wyoming, _C. g. brevicaudus_ has a slightly shorter tail, longer hind foot, greater basal and condylobasilar lengths, greater zygomatic and lambdoidal breadths and conspicuously longer nasals. In comparison with three adult _C. g. loringi_ from Elk River, Sherburne County, Minnesota, _C. g. brevicaudus_ has a greater total length, longer hind foot, greater basal length, conspicuously greater zygomatic and lambdoidal breadths, much longer nasals, and a narrower rostrum. _Clethrionomys gapperi brevicaudus_, although isolated geographically and although morphologically more distinct than many of the currently recognized subspecies of _C. gapperi_, is probably best arranged as a subspecies of _C. gapperi_ rather than as a full species. In certain characters, such as interorbital breadth and breadth of rostrum, it is intermediate between _C. g. galei_ and _C. g. loringi_, but it resembles _C. g. galei_ more than it does any other named kind. _Specimens examined._--Total, 66. Unless otherwise indicated, specimens from Wyoming are in the University of Kansas Museum of Natural History and specimens from South Dakota are in the University of Michigan Museum of Zoology. Specimens are distributed as follows: +Wyoming+: _Crook County_: 3 mi. NW Sundance, 5900 ft., 3. _Weston County_: 1-1/2 mi. E Buckhorn, 6150 ft., 21; 12 mi. SE Newcastle, 1 (Univ. Michigan). +South Dakota+: _Pennington County_: 1/2 mi. E Rochford, 1; 17 mi. NW Custer, 1; 16 mi. NW Custer, 20; 16 mi. SW Rapid City, 1; 3 mi. SE Hill City, 2; 4 mi. SE Hill City, 13; 5 mi. SE Hill City, Harney Peak, 7240 ft., 1. _Custer County_: 1-1/2 mi. E Sylvan Lake, 1. +Clethrionomys gapperi uintaensis+ Doutt 1897. _Evotomys gapperi galei_, Bailey, Proc. Biol. Soc. Washington, 11:127 (part from Uinta Mts. of Wyoming), May 13. 1941. _Clethrionomys gapperi uintaensis_ Doutt, Proc. Biol. Soc. Washington, 54:161, Dec. 8. _Type locality._--Paradise Park, 10,050 feet, 45 miles by road northwest Vernal, Uintah County, Utah. _Range._--The Uinta Mountains of northern Utah and southwestern Wyoming. _Remarks._--From the description given by Doutt (Proc. Biol. Soc. Washington, 54:161, 1941) in his original description of this subspecies, it appears that he had available for comparisons, only subadult specimens of _C. g. galei_. As judged from the material of _C. g. uintaensis_ available to us (1 topotype, KU 38081, and 7 specimens from Uinta County, Wyoming, listed below) and from Doutt's (_op. cit._) description and measurements, the subspecies _C. g. uintaensis_ is but weakly differentiated from _C. g. galei_. No marked cranial differences are evident between the two subspecies; the differences in pelage noted by Doutt (_op. cit._:161), however ("Similar to _Clethrionomys gapperi galei_ from Ward, Colorado, but head and cheeks grayer; sides and back paler; belly whiter."), do seem to be valid. On the basis of these differences in pelage and the geographic isolation of the range, we judge that _uintaensis_ should be retained as a subspecies of _C. gapperi_. It is clear, however, that _C. g. uintaensis_ is less distinct from _C. g. galei_ than are the other adjacent subspecies. _Specimens examined._--Total, 8, all in the University of Kansas Museum of Natural History, distributed as follows: +Wyoming+: _Uinta County_: 9 mi. S Robertson, 8000-8400 ft., 3; 9 mi. S and 2 mi. E Robertson, 8000 ft., 2; 11-1/2 mi. S and 2 mi. E Robertson, 9200 ft., 1; 14 mi. S and 2 mi. E Robertson, 9000 ft., 1. +Utah+: _Uintah County_: Paradise Park, 21 mi. W, 15 mi. N Vernal, 10,050 ft., 1. _Additional, marginal records_ (Durrant, Univ. Kansas Publ., Mus. Nat. Hist., 6:356, August 19, 1952).--+Utah+: _Rich Co._: Monte Cristo, 18 mi. W Woodruff, 8000 ft. _Salt Lake Co._: Emigration Canyon, 8 mi. above forks, 6,000 ft.; Silver Lake Post Office (Brighton), 9,500 ft. _Wasatch Co._: Wolf Creek Summit, 9,800 ft. _Daggett Co._: Beaver Dams, 10,500 ft. +Clethrionomys gapperi gauti+, new subspecies _Type._--Male, adult, skin and skull; No. 133515, Biological Surveys Collections, United States National Museum, from Twining, 10,700 ft., Taos County, New Mexico; obtained on August 7, 1904, by James H. Gaut, original number 3086. _Range._--The Rocky Mountains of north-central New Mexico and south-central Colorado. _Diagnosis._--A brightly colored _Clethrionomys gapperi_; dorsal stripe near Chestnut (capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) with an underwash of near Light Ochraceous-Buff and a mixture of black-tipped guard hairs giving an over-all effect of between Tawny and Russet; braincase relatively large; zygomatic width and lambdoidal width large; nasals long. _Comparisons._--As compared with topotypes of _C. g. galei_, the color is lighter, the dorsal reddish stripe slightly narrower, sides brighter, with a wash of Light Ochraceous-Buff, grading ventrally into a slight wash of Pale Ochraceous-Buff, instead of a silvery-white venter characteristic of _C. g. galei_; zygomatic and lambdoidal breadths are greater, nasals slightly shorter, auditory bullae slightly more inflated, teeth larger, and braincase larger. As compared with topotypes of _C. g. limitis_, _C. g. gauti_ is darker, has a greater zygomatic breadth, longer upper tooth-row, longer nasals, and narrower rostrum. _Measurements._--External and cranial measurements of the type, and the average and extreme measurements of four adult males and one adult female from the type locality (including the type) and five miles south of the type locality are: Total length, 144, 147 (140-152); tail, 40, 42 (39-45); hind foot, 20, 19.3 (19-20); condylobasilar length, 22.3, 22.9 (22.2-24.0); zygomatic breadth, 13.6, 13.7 (13.5-14.0); lambdoidal breadth, 11.9, 11.7 (11.4-12.0); alveolar length of upper cheek-teeth, 5.1, 5.2 (5.1-5.4); interorbital breadth, 4.0, 3.9 (3.8-4.0); length of nasals, 7.0, 7.2 (7.0-7.6); breadth of rostrum, 2.9, 3.1 (2.9-3.4); length of incisive foramina, 4.8, 5.1 (4.8-5.3). _Remarks._--Two specimens from a locality 21 mi. W and 3 mi. N Saguache, Saguache County, Colorado, although referred to this subspecies on the basis of paler pelage, inflation of auditory bullae, and heavier teeth, show characters of _C. g. galei_ in the narrowness across the zygomata and lambdoidal crest. Four specimens from Silverton (1 adult and 3 young adults) are referable to this subspecies on the basis of color of pelage and cranial proportions but are smaller than either _C. g. gauti_ or _C. g. galei_. The specimen from Pecos Baldy, Pecos Mountain, San Miguel County, New Mexico, referred by Bailey (N. Amer. Fauna, 52:192) to _Clethrionomys gapperi galei_, is here referred to _C. g. gauti_ on geographical grounds. The name _gauti_ is proposed in honor of the collector of the type specimen, James H. Gaut. _Specimens examined._--Total, 14, distributed as follows and, unless otherwise stated, in the Biological Surveys Collection: +Colorado+: _Saguache County_: 21 mi. W and 3 mi. N Saguache, N 38 deg., 106 deg. 31', 9100 ft., 2 (Univ. Kansas Mus. Nat. Hist.). _San Juan Co._: Silverton, 4. +New Mexico+: _Taos County_: Twining, 10,700 ft., 3; 5 mi. S Twining, 11,400 ft., 3. _Sandoval County_: Goat Peak, Jemez Mountains, 1. _Colfax County_: 15 mi. SW Cimarron, 9000 ft., 1 (Amer. Mus. Nat. Hist.). _Additional records._--+New Mexico+: _San Miguel Co._: Pecos Baldy, Pecos Mountain, 1 (Bailey, N. Amer. Fauna, 52:192, 1932). +Clethrionomys gapperi limitis+ (Bailey) 1913. _Evotomys limitis_ Bailey, Proc. Biol. Soc. Washington, 26:133, May 21. _Type locality._--Willow Creek, a branch of the Gilita, 8500 ft., Mogollon Mountains, Catron County, New Mexico. _Range._--Known from the Mogollon, San Mateo, and Magdalena mountains of western New Mexico. _Remarks._--Bailey (Proc. Biol. Soc. Washington, 26:133, May 21, 1913) described this animal as a species and gave as general characteristics: "Size slightly larger than _E._ [= _Clethrionomys gapperi_] _galei_; colors duller, grayer and less buffy; skull and dentition heavier." He further characterized the skull as: "Larger, heavier and conspicuously more ridged than in _galei_; bullae large and especially deep; dentition heavy throughout." The type of _C. limitis_, as judged from the measurements given by Bailey (_loc. cit._), is an exceptionally old male. Our comparison of six adult topotypes with a series of _C. g. galei_ from Wyoming (18 adults from 3 mi. SSE Browns Peak, 10,000 ft., Albany County, in Univ. Kansas Mus. Nat. Hist.) and with three near-topotypes of _C. g. galei_ (3 mi. S Ward, 9000 ft., Boulder County, Colorado, in Univ. Kansas Mus. Nat. Hist.) revealed that most of the differences noted by Bailey (_loc. cit._) are not evident when individuals of comparable ages are examined. Some specimens of _C. g. galei_ exceed _C. limitis_ in ridging of the skull and size of the teeth although conspicuous ridges and large teeth are supposedly distinctive of _C. limitis_. The bullae, although averaging larger in _C. limitis_, can be matched in size by those of specimens of _C. g. galei_ from Wyoming. The differences evident between _C. limitis_ and _C. g. galei_ are of the kind and degree that serve to separate subspecies in the species _Clethrionomys gapperi_ and, although actual evidence of intergradation is lacking, we think that the relationships of _limitis_ are better expressed by arranging it as a subspecies of _C. gapperi_ than by retaining it as a full species. _Specimens examined._--Total, 7, all in the Biological Surveys Collection, distributed as follows: +New Mexico+: _Catron County_: Willow Creek, 8500 ft., Mogollon Mountains, 4. _Socorro County_: San Mateo Peak, 10,000 ft., San Mateo Mountains, 2; Copper Canyon, 9000 ft., Magdalena Mountains, 1. +Clethrionomys gapperi arizonensis+, new subspecies _Type._--Female, adult, skin and skull; No. 158401, Biological Surveys Collection, United States National Museum; from Little Colorado River, 8300 ft., White Mountains, Apache County, Arizona; obtained September 12, 1908, by C. Birdseye, original number 152. _Range._--Known only from the White Mountains of eastern Arizona. _Diagnosis._--Dorsal stripe near Chestnut, with an underwash of between Tawny and Russet, and a mixture of black-tipped hairs, resulting in an overall effect of near Chestnut. Skull wide across zygomatic arches and narrow across mastoids; rostrum narrow and posterior border of palate straight. _Comparisons._--This subspecies needs close comparison only with the adjacent subspecies _C. g. limitis_. As compared with topotypes of _limitis_, _C. g. arizonensis_ has darker pelage, narrower rostrum, greater width across zygomatic arches, lesser lambdoidal breadth, longer nasals, wider palate, and more inflated auditory bullae. The posterior border of the hard palate is straight in five skulls of the series that are complete (two skulls have the palatal regions broken); all _C. g. limitis_ examined have a median posterior projection on the posterior border of the hard palate. _Measurements._--External and cranial measurements of the type, and the average and extreme measurements of three adult males and two adult females from the type locality (including the type) are: Total length, 160, 145.6 (137-160); tail, 44, 40.8 (37-46); hind foot, 18.5, 19.3 (18-20); condylobasilar length, 23.3, 22.8 (22.1-23.5); zygomatic breadth, 13.8, 13.4 (12.6-13.8); lambdoidal breadth, 11.5, 11.4 (11.0-11.6); alveolar length upper cheek-teeth, 5.5, 5.4 (5.2-5.5); interorbital breadth, 3.8, 3.9 (3.8-4.0); length of nasals, 7.6, 7.1 (6.9-7.6); breadth of rostrum, 3.1, 3.1 (3.0-3.2); length of incisive foramina, 5.5, 5.2 (5.0-5.5). _Remarks._--Hall and Davis (Proc. Biol. Soc. Washington, 47:55, February 9, 1934) reported 12 specimens of red-backed mice from Hannagan Meadow, 9500 to 9600 ft., and ten from Hannagan Creek, 8600 ft., all in Greenlee County, Arizona. Although they pointed out most of the cranial differences here described as diagnostic of _C. g. arizonensis_, they did not name the animals as new since they had no seasonally comparable materials; thus they were unable to evaluate the differences noted in pelage. We have not examined the material referred to by Hall and Davis (_loc. cit._), but, on the basis of their description, here refer it to _C. g. arizonensis_. _Specimens examined._--Total, 7, all from the type locality and all in the Biological Surveys Collection in the United States National Museum. Grateful acknowledgment is made of the opportunity to study the specimens from New Mexico and Arizona in the Biological Surveys Collection of the United States National Museum and the material from South Dakota in the University of Michigan Museum of Zoology, as well as for the financial support afforded one of us (Cockrum) by the University of Kansas from its Research appropriation. Cockrum's work was part of a larger investigation of the geographic distribution of all North American native mammals, aided by a contract between the Office of Naval Research, Department of the Navy, and the University of Kansas (NR. 161-791). Also, assistance with some of field work was given by the Kansas University Endowment Association. _Transmitted June 21, 1952._ [Illustration: printers mark] 24-4369 Transcriber's Notes. This file was derived from scanned images. The original text is presented. Emphasis Notation: _text_ - italicized +text+ - bold ~text~ - small caps End of the Project Gutenberg EBook of Geographic Variation in Red-backed Mice (Genus Clethrionomys) of the Southern Rocky Mountain Region, by E. Lendell Cockrum and Kenneth L. Fitch *** END OF THIS PROJECT GUTENBERG EBOOK RED-BACKED MICE *** ***** This file should be named 32679.txt or 32679.zip ***** This and all associated files of various formats will be found in: http://www.gutenberg.org/3/2/6/7/32679/ Produced by Chris Curnow, Tom Cos, Joseph Cooper and the Online Distributed Proofreading Team at http://www.pgdp.net Updated editions will replace the previous one--the old editions will be renamed. Creating the works from public domain print editions means that no one owns a United States copyright in these works, so the Foundation (and you!) can copy and distribute it in the United States without permission and without paying copyright royalties. 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