_Description._--_Color pattern_: Crown Sayal Brown washed with Cinnamon Buff; facial stripes Fuscous Black mixed with Clay Color; anterior margin of ear Ochraceous-Orange; hairs inside posterior part of pinna Ochraceous Buff; posterior margin of ear and postauricular patch grayish white; dorsal dark stripes Fuscous Black more or less mixed with Ochraceous Buff; medial dorsal light stripes Pale Smoke Gray with Ochraceous Buff along margins; lateral dorsal light stripes grayish white or white with Ochraceous Buff along margins; sides Ochraceous Buff; rump and thighs Smoke Gray washed with Ochraceous Buff; dorsal surface of tail black interspersed with Ochraceous Buff; ventral surface of tail Ochraceous-Orange, with black along margin and Light Ochraceous Buff along outermost edge; antipalmar and antiplantar surfaces of feet Light Buff; underparts creamy white sometimes washed with Ochraceous Buff. _Skull_ and _Baculum_: Large but of same proportions as in other subspecies of _E. minimus_. _Comparisons._--From _E. m. operarius_, the subspecies from south-central Wyoming, _E. m. silvaticus_ differs in: Underside of tail lighter; general tone of upper parts grayer; sides lighter; skull and baculum of same size and proportions. For comparisons with _E. m. pallidus_ and _E. m. confinis_, see the accounts of those subspecies. _Remarks._--Intergradation between _E. m. silvaticus_ and _E. m. pallidus_ has already been discussed under the account of _E. m. pallidus_. _Specimens examined._--Total number, 42. _Crook Co._: 15 mi. N Sundance, Black Hills Nat. Forest, 5,500 ft., 6; 15 mi. ENE Sundance, 3,825 ft., 1; 3 mi. NW Sundance, 5,900 ft., 14; 1 mi. N Sundance, Black Hills Nat. Forest, 1. _Weston Co._: 1-1/2 mi. E Buckhorn, 6,150 ft., 19; SE Newcastle, 1 (MM). _Additional records_ (Howell 1929:57): _Crook Co._: Devils Tower; Sundance. Eutamias minimus operarius Merriam _Eutamias amoenus operarius_ Merriam, Proc. Biol. Soc. Washington, 18:164, June 29, 1905. _Eutamias minimus operarius_, Howell, Jour. Mamm. 3:183, August 4, 1922. _Type._--Female, adult, skull and skin, No. 129808 (BS); from Gold Hill, 7,400 ft., Boulder County, Colorado; obtained on October 8, 1903, by Vernon Bailey; original No. 8160. _Diagnosis._--Size large; general tone of upper parts dark reddish brown; sides Tawny or Ochraceous Tawny; baculum large, as in _E. m. pallidus_.