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°, 106° 31´, 9100 ft., 2 (Univ. Kansas Mus. Nat. Hist.). San Juan Co.: Silverton, 4.