Specimens from one mile southwest of Fairbanks and from Fairbanks, Alaska, show intergradation with _Zapus hudsonius alascensis_ in coloration (more brown, less black), but in small size, short, broadly rounded incisive foramina, and in size and shape of the auditory bullae are nearest to _Z. h. hudsonius_ to which they are here assigned. Intergradation with _Zapus hudsonius alascensis_ is noted also in specimens from McIntyre Creek, Yukon. They are like _Z. h. alascensis_ in the size and shape of the auditory bullae and in the more elongate incisive foramina, but in the coloration, size of the pterygoid fossae, and breadth of the braincase are more nearly like _Z. h. hudsonius_ and are here referred to this geographic race. In British Columbia, in specimens from 1 mi. NW junction of Irons Creek and Laird River as well as in those from Hot Springs, 3 mi. WNW junction of Trout River and Laird River, and in those from 1/4 mi. S of the junction of the same rivers, three way intergradation occurs. These animals are like _Zapus hudsonius alascensis_ in color and in length of tail. They agree with _Zapus hudsonius tenellus_ in shape of nasals. In degree of inflation of auditory bullae, in length and width of incisive foramina, and in shape of pterygoid fossae they are as in _Z. h. hudsonius_ to which they are here assigned. _Specimens examined._--Total, 230, distributed as follows: ALASKA: Fairbanks, 1 (USNM); _1 mi. SW Fairbanks, 440 ft._, 1. ALBERTA: Conibear Lake, Wood Buffalo Park, 1 (NMC); Assineau River, 1920 ft., 10 mi. E and 1 mi. N Kinuso, 1; Mountain Rapid, Athabasca River, 1 (USBS); _Brule Rapid, Athabasca River_, 1 (USBS); _25 mi. above Pelican Rapid, Athabasca River_, 1 (USBS); Lac la Nonne, 7 (NMC); _Swift Current, Athabasca River_, 1 (USBS); _junction Lac la Biche River and Athabasca River_, 1 (USBS); 30 mi. above Athabasca Landing, Athabasca River, 1 (USBS). BRITISH COLUMBIA: 1 mi. NW junction Irons Creek and Laird River, 3; Hot Springs, 3 mi. WNW junction Trout River and Laird River, 1; _1/4 mi. S junction Trout River and Laird River_, 1. MANITOBA: York Factory, 2 (USBS); Shamatawa River, 1 (USBS); Oxford House, 15 (USBS); _Robinson Portage_, 4 (USBS); _Echamamish_, 1 (USBS); Norway House, 1 (USBS); _Swan River_, 1 (NMC); Bird, 1 (NMC); _Aimie Lake_, 2 (NMC); Albert's Lake, Flin Flon, 2 (NMC); Portage La Prairie Prov., Delta, 1 (UM). MACKENZIE DISTRICT: Fort Resolution, 3 (USBS); Fort Smith, 3 (USBS).