_Mustela washingtoni_, Miller, U. S. Nat. Mus. Bull., 79:98, December 31, 1912. _Mustela frenata washingtoni_, Hall, Carnegie Instit. Washington Publ. 473:106, November 20, 1936. _Type._--Male, adult, skin and skull; no. 76322, U. S. Nat. Mus., Biol. Surv. Coll.; Trout Lake, Mt. Adams, Klickitat (?) County, Washington; December 15, 1895; obtained by D. N. Kaegi; original no. 2. The skull is unbroken. The left incisors above are missing. Otherwise the teeth are present and entire. The skin is well made, in brown winter pelage, lacks collector's measurements, has no bones in the feet, but by large size is judged to be a male. _Range._--Altitudinally from near 2000 feet at Trout Lake up to the highest parts of the Cascade Range from Mount Jefferson, Oregon, north to Mount Rainier, Washington; Upper Sonoran Life-zone to Arctic Alpine Life-zone. See figure 29 on page 221. _Characters for ready recognition._--Differs from _M. f. altifrontalis_ in lighter color of upper parts and underparts, latter ranging from Buff-Yellow to Naples Yellow rather than near (14 _a_ to 16 _c_) Ochraceous-Buff, in shallower skull in both sexes (see measurements), in males, a longer preorbital region, narrower skull with shorter bullae, and in females, a smaller skull with interorbital breadth averaging less than 24 per cent of basilar length; from _M. f. nevadensis_ in absence of light color of underparts on ventral face of tail, in skulls of males, by longer preorbital region and narrower skull across mastoid processes and zygomatic arches, in skulls of females, by shorter preorbital region, and smaller bullae (see measurements); from _M. f. effera_ in absence of light color of underparts on ventral face of tail, in skulls of males, by linear measurements averaging 7 (5-12) per cent larger, and relative to basilar length, longer in the preorbital region and narrower across mastoid processes and zygomatic arches; from _M. f. oregonensis_ in absence of frontonasal white patch, longer skull in males, which in percentage of basilar length has, on the average, orbitonasal length amounting to more than 35, mastoid breadth less than 55, and zygomatic breadth less than 63, and in females, smaller skull with least width of palate less than length of P4, upper tooth-rows less than 38-1/2 per cent of basilar length, bullae smaller, averaging less than 13.4 in length.