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.
An attempt to collect specimens of T. b. howelli, in March, 1957, by Richard S. Miller and the writer was unsuccessful.
Specimens examined.—Total 2. Mesa Co.: Grand Junction, 4600 ft., 1 (USNM); Sieber Ranch, Little Doloris River, 1 (ERW).
Thomomys bottae pervagus Merriam
Thomomys aureus pervagus Merriam, Proc. Biol. Soc. Washington, 14:110, July 19, 1901; Cary, Proc. Biol. Soc. Washington, 20:26, March 27, 1907; Warren, Colorado College Publ., 33:77, January, 1908; Warren, Mammals of Colorado, p. 79, 1910, part; Cary, N. Amer. Fauna, 33:137, August 17, 1911, part.