Type.—Female, adult, skull and skin, No. 20050 Mus. Nat. Hist., Univ. Kansas; from 3 mi. NW Sundance, 5900 ft., Crook County, Wyoming; obtained on July 4, 1947, by H. W. Setzer; original No. 1692.

Range.—Bear Lodge Mountains in northeastern Wyoming and the Black Hills of South Dakota.

Diagnosis.—Size large (see measurements); general tone of upper parts drab; sides Ochraceous Buff (capitalized terms are of Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912); lateral stripes Fuscus Black washed with Ochraceous Tawny; ventral side of tail near (14' h) Ochraceous Orange and fringed with black.

Comparisons.—From Eutamias minimus pallidus (specimens from Buffalo in Johnson County, Ivy Creek, Rockypoint, Middle Butte, and South Butte in Campbell County, all in Wyoming, and Harrison, Sioux County, Nebraska), the subspecies to the southward, westward, and northward, E. m. silvaticus differs in: General tone of upper parts markedly darker, more reddish and less grayish; dorsal stripes darker; crown markedly darker. External measurements, and measurements and characters of the skull of the two subspecies, do not differ significantly. Unless otherwise specified all comparative material is in the Museum of Natural History of the University of Kansas.

From Eutamias minimus cacodemus (topotypes in the United States National Museum), the subspecies to the southeastward, E. m. silvaticus differs in the same manner in which it differs from E. m. pallidus, but the degree of difference is greater because E. m. cacodemus is even paler than E. m. pallidus.

From Eutamias minimus confinis (specimens from 17½ mi. E and 4½ mi. S Shell, 8500 ft., Big Horn County, Wyoming), E. m. silvaticus differs in: General tone of upper parts darker, more reddish and less grayish; sides of rump more reddish and less grayish; underside of tail more tawny; skull distinctly longer and broader across zygomata.

From Eutamias minimus borealis (specimens from 1 mi. NW of junction of Irons Creek and Laird River; N side Muskwa River, 4 mi. W Ft. Nelson, 1200 ft.; E side Minaker River, 1 mi. W Trutch; Beatton River, 115 mi. S Ft. Nelson; 5 mi. W and 3 mi. N Ft. St. John; S side Toad River, 10 mi. S and 21 mi. E Muncho Lake; all in British Columbia; and from Assineau River, 1920 ft., 10 mi. E and 1 mi. N Kinuso, Alberta), E. m. silvaticus differs in: Under side of tail more reddish; dorsal stripes less blackish; sides slightly paler (less tawny); nasals distinctly shorter; skull distinctly shorter.

Measurements.—Average and extreme measurements of three adult males and 11 adult females of E. m. silvaticus from the type locality are, respectively, as follows: Total length, 190 (189-190), 207 (202-220); length of tail, 85 (81-90), 97 (82-105); length of hind foot, 31 (30-33), 32 (31-34); length of ear, 14 (13-16), 15 (14-17); weight, 45.7 (44.6-46.5), 55.7 (50.0-68.0); greatest length of skull, 32.0 (31.5-32.6), 32.3 (31.5-33.1); zygomatic breadth, 18.5 (18.5-18.5), 18.6 (18.2-19.0); least interorbital constriction, 6.9 (6.8-7.1), 7.0 (6.4-8.1); length of nasals, 9.4 (9.2-9.6), 9.6 (9.3-10.1).

Measurements of the type.—Total length, 206; length of tail, 90; length of hind foot, 32; length of ear, 15; weight, 59.3; greatest length of skull, 32.6; zygomatic breadth, 18.6; least interorbital constriction, 6.4; length of nasals, 9.3.

Specimens examined.—Total number, 28. Specimens from South Dakota are in the United States National Museum, and those from Wyoming are in the Museum of Natural History of the University of Kansas.

South Dakota: Custer Co.: Custer, 3; Lawrence Co.: Deadwood, 10.

Wyoming: Crook County: 3 mi. NW Sundance, 5900 ft., 14; 15 mi. ENE Sundance, 3825 ft., 1.

Acknowledgment is made of assistance, with the field work, received from the Kansas University Endowment Association.

Museum of Natural History, University of Kansas, Transmitted December 8, 1951.