Tamias minimus Bachman, Jour. Acad. Nat. Sci. Philadelphia, 8(pt. 1):71, 1839.
Eutamias minimus, Miller and Rehn, Proc. Boston Soc. Nat. Hist., 30:42, December 27, 1901.
Type.—Obtained on Green River, near mouth of Big Sandy Creek, Sweetwater County, Wyoming. Age, sex, collector, and date when obtained, not surely known.
Diagnosis.—Size small; general tone of upper parts pale grayish brown; baculum small.
Description.—Color pattern: Crown Pinkish Buff mixed with grayish white; facial stripes Snuff-Brown mixed with black; anterior margin of ear Drab washed with Cinnamon; hairs inside posterior part of pinna Light Pinkish Cinnamon; posterior margin of ear and postauricular patch grayish white; median dorsal dark stripe black with Sayal Brown along margins; lateral pair of dark stripes Sayal Brown more or less mixed with Fuscous; pairs of light dorsal stripes grayish white and tinged with Buff; rump and thighs Smoke Gray; dorsal surface of tail Fuscous Black mixed with Cinnamon-Buff; ventral surface of tail Sayal Brown or Clay Color, Blackish Brown mixed with Cinnamon-Buff around margins; antiplantar and antipalmar surfaces of feet Pale Pinkish Buff; underparts creamy white. Skull and Baculum: Small but proportionally the same as in other subspecies of E. minimus.
Comparisons.—From E. m. consobrinus, the subspecies to the west and south, E. m. minimus differs in: Over-all tone of upper parts lighter; underside of tail lighter.
From E. m. pallidus, the subspecies to the north and northeast, E. m. minimus differs in: Size smaller; skull shorter and narrower; mandible shorter and shallower; baculum shorter; slightly paler.
From E. m. confinis, the subspecies in the Big Horn Mountains, E. m. minimus differs in: Size smaller; skull shorter and narrower; mandible shorter and shallower; baculum shorter; paler.
From E. m. operarius, the subspecies to the east and southeast, E. m. minimus differs in: Size smaller; skull shorter and narrower; mandible shorter and shallower; baculum shorter; paler.
Remarks.—E. m. minimus is the smallest of the chipmunks that occur in Wyoming. This pale little squirrel is found in the Red Desert in Sweetwater County, where the features distinctive of the subspecies are most strongly developed. Specimens from western Sweetwater County and northwestern Uinta County are intergrades between E. m. minimus and E. m. consobrinus and are referable to E. m. minimus.