_Specimens examined._--Total 93, as follows: _Yukon Territory_: McIntyre Creek, 2250 ft., 3 mi. NW Whitehorse, 26; W side Lewes River, 2150 ft., 2 mi. S Whitehorse, 4; 5 mi. W Teslin River, 2400 ft., 16 mi. S and 53 mi. E Whitehorse, 7; E side Teslin River, 2300 ft., 16 mi. S and 59 mi. E Whitehorse, 1. _British Columbia_: 1 mi. NW jct. Irons Creek and Liard River, 8; Hot Springs, 3 mi. WNW jct. Trout River and Liard River, 3; N side Liard River, ½ mi. W jct. Liard River and Trout River, 1; ¼ mi. S jct. Trout River and Liard River, 13; S side Toad River, 10 mi. S and 21 mi. E Muncho Lake, 2; Summit Pass, 4200 ft., 10 mi. S and 70 mi. W Fort Nelson, 2; E side Minaker River, 1 mi. W Trutch, 19; Beatton River, 115 mi. S Fort Nelson, 1; 5 mi. W and 3 mi. N Fort St. John, 2. _Alberta_: Assineau River, 1920 ft., 10 mi. E and 1 mi. N Kinuso, 4. _Remarks._--Adults among the specimens listed above vary but little; one female from Assineau River in Alberta is notably more reddish than others taken elsewhere. Average and extreme measurements of nine adults of both sexes of _M. p. drummondii_ from E side Minaker River, 1 mi. W Trutch, British Columbia, are as follows: Total length, 157 (148-165); length of tail, 42 (37-46); condylobasal length, 25.1 (24.7-26.0); basal length, 24.2 (23.4-25.0); length of nasals, 6.8 (6.4-7.2); zygomatic breadth, 14.4 (13.9-14.7); breadth across auditory bullae, 12.4 (12.0-12.7); alveolar length of upper molariform tooth-row, 6.1 (6.0-6.2); Nine adults of both sexes from McIntyre Creek, 2250 ft., 3 miles northwest of Whitehorse, Yukon Territory, have the following measurements: 153 (147-168); 40 (33-47); 24.9 (24.2-25.5); 24.0 (23.6-24.6); 6.6 (6.2-7.2); 14.4 (13.9-15.1); 12.1 (11.7-12.5); 6.1 (6.0-6.2). Microtus _cf._ cantator Anderson Yukon Singing Mouse _Microtus cantator_ Anderson, Nat. Mus. Canada, Bull. No. 102, Biol. Ser. No. 31:161, [for 1946], January 24, 1947. (Type "taken in tundra-slide above timber-line on mountain top near Tepee Lake on north slope of St. Elias Range," Yukon Territory, Canada.) _Specimen examined._--One from _Alaska_: Fish Creek, 3400 ft., 5 mi. N and 1 mi. E Paxson.