_Putorius arcticus polaris_ Barrett-Hamilton, Ann. and Mag. Nat. Hist., 13 (ser. 7):393, May, 1904. _Mustela erminea_, Manniche, Meddelelser on Grønland, 45:80-85, 1 fig., 1910. _Mustela arctica polaris_, Miller, U. S. Nat. Mus. Bull., 79:97, December 31, 1912. _Mustela erminea polaris_, Hall, Journ. Mamm., 26:179, July 19, 1945. _Type._--Probably female, skin only; no. 78. 6. 19. 11, Brit. Mus. Nat. Hist.; Gap Valley, 7-1/4 miles northeast Cape Brevoort, 82° N, 59° 20´ W, Northwestern Greenland; June 15 or 16, 1876; obtained by Lewis A. Beaumont. The skin is in full, fresh summer pelage, fairly well stuffed except for the tail which is unstuffed; the whole is in a good state of preservation. _Range._--North coast, and east coast as far south as Turner Sound (between 69 and 70 degrees) of Greenland. See figure 25 on page 95. _Characters for ready recognition._--Differs from _M. e. arctica_ in lighter upper parts (near [_j_] Buckthorn Brown rather than Raw Umber or darker) and more intensely-colored underparts that are Buff Yellow rather than Sulphur Yellow, Colonial Buff, or Primrose Yellow; from _M. e. semplei_ in color in same fashion as from _arctica_ and in larger size of skull. _Description._--_Size._--Male: One subadult and two adults (one ad. from Scøresby Sound and other two from Ymer Island) measure as follows, the average being given first: Total length, 318 (301, 320, 315); length of tail, 72 (69, 70, 73); length of hind foot, 46.5 (44, 46, 47). Female: No measurements taken in the flesh available but hind foot, measuring 33.5 in the dried state and therefore approximately 35 in life. _Color._--As described in _Mustela erminea arctica_ except that upper parts in summer near (_j_) Buckthorn Brown and tone 4 of Dark Fawn of plate 307 to tone 1 of Raw Umber of plate 301 of Oberthür and Dauthenay. Underparts Buff-Yellow. Least width of color of underparts averaging, in 3 males, 66 (57-72) per cent of greatest width of color of upper parts. Black tip of tail in same males averaging 71 (70-72) mm. which is 99 (99-104) per cent of length of tail-vertebrae. The lighter-colored upper parts and more intensely yellow underparts are the distinguishing features of the subspecies _polaris_ in comparison with other races of American _M. erminea_.