_Mustela cicognanii mortigena_ Bangs, Bull. Mus. Comp. Zoöl., 54:511, July, 1913. Type from Bay St. George, Newfoundland. _Mustela cicognanii_, Sheldon, Journ. Mamm., 13:201, August 9, 1932. _Mustela cicognanii richardsonii_, Miller, U. S. Nat. Mus. Bull., 79:95, December 31, 1912; Hall, Univ. California Publ. Zoöl., 40:368, November 5, 1934. _Mustela cicognanii cicognanii_, Hall, Canadian Field-Nat., 52:108, October, 1938. _Mustela erminea richardsonii_, Hall, Journ. Mamm., 26:77, February 27, 1945; Hall, Journ. Mamm., 26:180, July 19, 1945. _Type._--Male, age unknown, skin; no. 43.3.3.4, British Museum of Natural History; probably from Fort Franklin, Canada; presented to British Museum on or before March 3, 1843; may be the type. In September, 1937, when I searched in the British Museum for the skull, I found no trace of it nor mention of it in catalogues. The skin is in white, winter pelage, mounted on a pedestal. See under remarks for _Mustela e. cicognanii_ for reasons for and reasons against regarding this specimen as the holotype. _Range._--Hudsonian and Canadian life-zones of the greater part of Canada from the Atlantic to the Pacific. See figure 25 on page 95. _Characters for ready recognition._--Differs from _M. e. arctica_, _polaris_, _semplei_ and _haidarum_, in both sexes, by proximal two-thirds of under side of tail colored same as upper parts rather than same as underparts, and interorbital breadth less, rather than not less, than distance between glenoid fossa and posterior border of external auditory meatus; from _M. e. bangsi_, in that, in both sexes, least width of color of underparts averages two-fifths rather than about a third of greatest width of color of upper parts, and in that skulls of males are a fourth heavier, basilar length averaging more than 40; from _M. e. cicognanii_, in both sexes, in that least width of color of underparts averages two-fifths instead of less than a third of greatest width of color of upper parts, in females by 20 per cent heavier skull (1.1 versus 0.92), in males by skull more, rather than less, than 1.9 grams, and basilar length more, instead of less, than 38; from _M. e. invicta_, in males, by skull more, instead of less, than 1.9 grams; mastoid breadth more, instead of less, than 19.9 mm.; depth of skull at anterior margin of braincase more, instead of less, than 12.4 mm.; in females, by same measurement of depth more, instead of less, than 10.1, and weight of skull averaging more, instead of less, than one gram; from _M. e. fallenda_ in both sexes upper lips white rather than brown, in males, hind foot more than 41, basilar length more than 38.3, in females hind foot more than 29, basilar length more than