_Diagnosis._--Size medium; pelage dark; sides dark; narrow cranial breadth; baculum distinguishable from that of any other species (E. palmeri excepted) by the combination of width of base more than 1/3 of length of shaft, distal 1/2 of shaft laterally compressed, and keel 1/4 of length of tip. =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 U. S. Nat. Mus., Biol. Surv. Coll.; from Blacks Fork, about 9,500 ft., Uinta Mountains, Utah; obtained on September 19, 1888, by Vernon Bailey; original No. 228. _Diagnosis._--Size medium; general tone of upper parts dark and shadowy; skull relatively small. _Description._--_Color pattern_: Head Pale Smoke Gray; facial stripes Fuscous Black to Snuff Brown; ear Fuscous Black; posterior margin of ear and postauricular patch grayish white; median dorsal dark stripe black with Sayal Brown along margins; lateral pair of dorsal dark stripes Sayal Brown or Fuscous Black mixed with Sayal Brown; outermost pair of dorsal dark stripes nearly absent; sides Sayal Brown mixed with Cinnamon; rump and thighs Sayal Brown mixed with Smoke Gray; antipalmar and antiplantar surfaces of feet Cinnamon-Buff; ventral surface of tail Ochraceous Tawny or Sayal Brown, with Fuscous Black around margin and Pinkish Buff around outermost edge; underparts creamy white with dark gray underfur. _Skull_: Large, with moderately inflated braincase and well developed zygomata. _Baculum_: One of the largest in the species. _Comparisons._--From _Eutamias umbrinus adsitus_, the subspecies to the south on the Wasatch Range, _E. u. umbrinus_ differs in: Sides lighter; rump browner; hairs around outermost edge of tail tawnier (in freshly molted tails); shorter inner mandibular length. From _E. u. inyoensis_, the subspecies to the west in central and northeastern Nevada and in northwestern Utah, _E. u. umbrinus_ differs in: General tone of upper parts lighter; sides lighter; total length more; interorbital region broader. For comparisons with _E. u. sedulus_, _E. u. fremonti_, and _E. u. montanus_, see the accounts of those subspecies. _Specimens examined._--Total number, 55. =Wyoming=: _Uinta Co._: 9 mi. S Robertson, 8,000 ft., 15; 10 mi. S and 1 mi. W Robertson, 8,700 ft., 5; 11-1/2 mi. S and 2 mi. E Robertson, 9,200 ft., 1; 2 mi. E and 12 mi. S Robertson, Ashley Nat. For., 1; 13 mi. S and 2 mi. E Robertson, 9,200 ft., 1.