_Color._--As described in _Mustela erminea richardsonii_ except that underparts not Sulphur Yellow but ranging from near (_e_) Colonial Buff through Marguerite Yellow to almost pure white; color of underparts extends distally on posterior sides of forelegs and onto toes but in many specimens interrupted at wrist by color of upper parts; color of underparts extends onto proximal three-fourths of under side of tail as length of tail is measured along tail-vertebrae; least width of color of underparts averaging, in 5 males, 79 (66-130) per cent of greatest width of color of upper parts. Black tip of tail in same males averaging 62 (60-70) mm. which is 92 (83-115) per cent of length of tail-vertebrae. The close correspondence in color-pattern of this weasel with the Arctic races, _arctica_, _polaris_, _semplei_ and _kadiacensis_ is noteworthy, and distinguishes it from weasels on the adjacent mainland and adjoining islands to the north and south. The color of the upper parts is darker than in the four Arctic races named. _Skull._--Male (7 adults): See measurements and plates 5-7. As described in _Mustela erminea richardsonii_ except that: Weight, 1.9 (1.7-2.0) grams; basilar length, 36.7 (35.6-37.5); length of tooth-rows more than length of tympanic bullae; breadth of rostrum measured across lacrimal processes more than a third of basilar length; interorbital breadth more than distance between glenoid fossa and posterior margin of external auditory meatus; zygomatic breadth barely less than distance between last upper molar and jugular foramen. Female (2 adults): See measurements and plates 11-13. As described in _Mustela erminea richardsonii_ except that: Weight, 1.3 and 1.4 grams; basilar length, 34.2; length of tooth-rows more or less than (about equal to) length of tympanic bulla; breadth of rostrum more than 30 per cent of basilar length; interorbital breadth not less than distance between glenoid fossa and posterior margin of external auditory meatus.