The skin is in process of molt, approximately nine-tenths of the incoming white pelage being in place. The skin is well made and in a good state of preservation. _Range._--Chichagof and Baranof islands, Alaska. See figures 25, 26 on pages 95, 134. _Characters for ready recognition_ (only males known).--Differs from _M. e. arctica_, in that proximal two-thirds of under side of tail colored same as upper parts rather than same as underparts, zygomatic breadth less than distance between last upper molar and jugular foramen; from _M. e. salva_ in that orbitonasal length and mastoid breadth total more than 35 mm., weight of skull and lower jaws more than 2.1 grams; from _M. e. alascensis_, by total length more than 317, black tip of tail more than 57 per cent of length of tail-vertebrae, interorbital breadth more than 10.3 and equal to, instead of less than, distance between glenoid fossa and posterior border of external auditory meatus; from _M. e. celenda_ by chest white (not mostly covered by brown patch), breadth of rostrum measured across lacrimal processes less than a third of basilar length; from _M. e. seclusa_ in zygomatic breadth more than distance between last upper molar and jugular foramen. _Description._--_Size._--Male: The type and an adult topotype measure, respectively, as follows: Total length, 330, 320; length of tail, 95, 95; length of hind foot, 45, 45. Female: No external measurements available. _Color._--As described in _Mustela erminea richardsonii_ except that least width of color of underparts averages, in two young female topotypes, 50 (49, 50) per cent of greatest width of color of upper parts. Black tip of tail in three young female topotypes averaging 54 (52-55) mm. which is 67 (63-69) per cent of length of tail-vertebrae. _Skull._--Male (illustrated by type and 1 ad. topotype): See measurements and plates 4-6. As described in _Mustela erminea richardsonii_ except that: Weight, 2.3 and 2.5 grams; basilar length, 39.6, and 40.5; interorbital breadth equal to distance between glenoid fossa and posterior border of external auditory meatus. Female: No adults available.