_Specimens examined._--Total number, 24, arranged by localities from north to south. Unless otherwise indicated, specimens are in the Museum of Vertebrate Zoölogy, University of California. =Alaska.= Juneau, 5[91]; Taku River, 1; Windham, 9; Mitkof Island, 1; St. John Harbor, Zarembo Island, 1; Wrangel, 1[91]; Helm Bay, Cleveland Peninsula, 1; Cleveland Peninsula, 2[91]; Revillagigedo Island, Carroll Inlet, 2[91]; Loring, 1[91]. =Mustela erminea salva= Hall Ermine Plates 2, 3, 4, 9, 10 and 11 _Mustela erminea salva_ Hall, Proc. Biol. Soc. Washington, 57:35, June 28, 1944; Hall, Journ. Mamm., 26:180, July 19, 1945. _Type._--Male, adult, skull only; no. 74641, Mus. Vert. Zoöl.; Mole Harbor, Admiralty Island, Alaska, December 27, 1936; obtained by A. Hasselborg. The skull (plates 2-4) shows malformation of the frontal sinuses owing to parasites and lacks osseous tissue where the parasitic infestation was localized. The skull is unbroken. The teeth all are present and entire. _Range._--Admiralty Island, Alaska. See figures 25, 26 on pages 95, 134. _Characters for ready recognition_ (known only from skulls).--Differs from males of _M. e. alascensis_ in overall depth of braincase which is more than 89 per cent of orbitonasal length; from _M. e. initis_, in males, in that orbitonasal length and mastoid breadth total less than 35 mm., weight of skull and lower jaws less than 2.1 grams; from _M. e. celenda_, in males, in that breadth of rostrum measured across lacrimal processes less than a third of basilar length. _Description._--_Size._--Male: An adult from Gambier Bay measures: Total length, 320; length of tail, 95; length of hind foot, 45 (41 in dry skin). Female: A subadult from Hawk Inlet, measures: Total length, 250; length of tail, 70; length of hind foot, 33. _Color._--As described in _Mustela erminea richardsonii_ except that least width of color of underparts in four individuals 40 (38-43) per cent of greatest width of color of upper parts. Black tip of tail, in two individuals for which external measurements are given, amounting to 50 and 40 mm. respectively which is 53 and 57 per cent of length of tail-vertebrae. _Skull._--Male (type and 4 adult topotypes): See measurements and plates 2-4. As described in _Mustela erminea richardsonii_ except that: Weight, 1.7 (1.5-1.9) grams; basilar length, 37.8 (36.4-39.5, extremes are in subadults); length of tooth-rows more or less (usually more) than length of tympanic bulla; interorbital breadth rarely more than distance between glenoid fossa and posterior border of external auditory meatus.