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.