_Specimens examined._--Total 114. _Colorado_: Montrose Co.: West Paradox Valley, 5 (CMNH); Bedrock, 5150 ft., 5 (ERW); Coventry, 6800 ft., 14 (12 ERW, 2 USNM). San Miguel Co.: 19 mi. N Dove Creek, 6100 ft., 1. Montezuma Co.: _Ashbaugh's Ranch (T.36N, R.18W) 5350 ft._, 5 (4 ERW, 1 USNM); 15 mi. W Cortez (Sec. 2, T.35N, R.19W), 5400 ft., 8; Major Ranch, Cortez, 7 (CSU); _3 mi. SSW Cortez, 6400 ft._, 1; Ute Peak, 2 (CMNH); Four Corners, 1 (CMNH). Mesa Verde National Park: Upper Well, Prater Canyon, 7575 ft., 1; _3/4 mi. S, 1-3/4 mi. W Park Point, 8000 ft._, 3; _1/4 mi. N Middle Well 7500 ft._, 1; _Sec. 27, Head of E Fork, Navaho Canyon, 7900 ft._, 2; _1-1/4 mi. S, 1-3/4 mi. W Park Point, 8000 ft._, 1; _Middle Well, Prater Canyon, 7500 ft._, 9; _3 mi. N Rock Springs, 8200 ft._, 4; _1-1/2 mi. S, 2 mi. W Park Point, 8075 ft._, 1; _2-1/2 mi. N, 1/2 mi. W Rock Springs, 8100 ft._, 3; _2 mi. N, 1/4 mi. W Rock Springs, 7900 ft._, 2; _1/2 mi. N Far View Ruins, 7825 ft._, 1; _Far View Ruins, 7700 ft._, 1; _1 mi. NNW Rock Springs, 7500 ft._, 1; Rock Springs, 7400 ft., 1; Mancos River, 6200 ft., 9; _Mesa Verde_, 1 (USNM). La Plata Co.: 1 mi. N La Plata, 1; 3 mi. W Durango, 5; Florida, 6800 ft., 5; Bayfield, 1 (USNM); Bondad, 6 (CMNH); Archuleta Co.: 12 mi. W Pagosa Springs, 6700 ft., 2; Arboles, 1 (USNM). _New Mexico_: Rio Arriba Co.: La Jara Lake, 7500 ft., 2 (USNM). =Thomomys bottae howelli= Goldman _Thomomys bottae howelli_ Goldman, Jour. Washington Acad. Sci., 26:116, March 15, 1936; Warren, Mammals of Colorado, p. 161, 1942. _Thomomys aureus_, Cary, N. Amer. Fauna, 33:136, August 17, 1911, part. _Thomomys perpallidus aureus_, Bailey, N. Amer. Fauna, 39:74, November 15, 1915, part. _Holotype._--Adult female, skin and skull, number 75684, United States National Museum, obtained by Arthur H. Howell at Grand Junction, 4600 feet, Mesa County, Colorado, November 7, 1895. _Distribution._--Colorado Plateau Province of west-central Colorado and east-central Utah, in the Colorado River Valley east of the Green River (see fig. 1). _Distinctive characters._--Pale (Pinkish White 7.5YR 8/2); cranium flattened; nasals short and wide; posterior tongues of premaxillae long, thin, and attenuate (see fig. 3). _Comparisons._--Compared with _T. b. aureus_, _T. b. howelli_ differs as follows: paler; nasals shorter and wider; cranium more flattened; posterior extensions of premaxillae longer, thinner, and more acuminate. _Remarks._--_T. b. howelli_ most closely resembles _T. b. aureus_; however, since only one adult specimen of _T. b. howelli_ is known, it is impossible to appraise adequately its characters. Durrant (1952:211) records intergradation between _T. b. howelli_ and _T. b. osgoodi_, and between _T. b. howelli_ and _T. b. aureus_ in Utah.