_Description._--_Color pattern_: Crown Pale Smoke Gray mixed with Cinnamon; upper facial stripe Fuscous; other facial stripes Sayal Brown mixed with Fuscous or Fuscous Black; anterior margin of ear Ochraceous Tawny; posterior margin of ear and postauricular patch grayish white; median dorsal dark stripe Fuscous or black; other dorsal dark stripes black and mixed with gray, sometimes barely discernible; dorsal pair light stripes Smoke Gray; lateral pair of light stripes creamy white; rump and thighs Pale Smoke Gray mixed with Cinnamon; dorsal surface of tail Fuscous Black mixed with Tilleul Buff; underside of tail Cinnamon Buff or Pinkish Buff, Fuscous Black around margin and Tilleul Buff around outermost edge; antipalmar and antiplantar surfaces of feet Cinnamon Buff; underparts creamy white; sides Pinkish Cinnamon or Light Pinkish Cinnamon. _Skull_: Size medium; braincase well inflated; zygomata strong, moderately appressed to cranium. _Baculum_: Small; keel approximately 1/3 of length of tip. _Remarks._--Only a few specimens of this subspecies have ever been taken in Wyoming. Little is known about the habits of this chipmunk, which normally is shy and wary. _Specimens examined._--Total number, 6. _Sweetwater Co._: W side Green River, 1 mi. N Utah border, 6. _Additional records_ (Howell 1929:134): _Sweetwater Co._: Green River, 4 mi. NE Linwood, Utah. [Illustration: FIG. 3. Known occurrences and probable geographic distribution of the subspecies of _Eutamias umbrinus_ in Wyoming. See figure 1 for explanation of symbols. 1. _E. u. umbrinus_ 2. _E. u. fremonti_ 3. _E. u. montanus_] Eutamias umbrinus (J. A. Allen) _Diagnosis._--Size large; general tone of upper parts dark; base of baculum widened; outermost dorsal dark stripe barely discernible or lacking; skull rarely shorter than 34.0 mm. _Comparisons._--For comparisons with the other species of _Eutamias_ in Wyoming, see the accounts of _E. minimus_, _E. amoenus_, and _E. dorsalis_. _Remarks._--_E. umbrinus_ is the largest of the species of _Eutamias_ occurring in Wyoming. This species usually occurs in the Canadian and Hudsonian life-zones in the mountains of northwestern, southwestern, and south-central Wyoming. Eutamias umbrinus umbrinus (J. A. Allen) _Tamias umbrinus_ J. A. Allen, Bull. Amer. Mus. Nat. Hist. 3:96, June, 1890. _Eutamias umbrinus_, Miller and Rehn, Proc. Boston Soc. Nat. Hist., 30:45, December 27, 1901. _Type._--Male, adult, skull and skin, No. 186463 (NM); from Blacks Fork, about 9,500 ft., Uinta Mountains, Summit County, Utah; obtained on September 19, 1888, by Vernon Bailey; original No. 228. _Diagnosis._--Size medium; over-all tone of upper parts dark and shadowy; skull smallest of this species in Wyoming.