_Mustela erminea olympica_ Hall, Journ. Mamm., 26:81, February 27, 1945; Hall, Journ. Mamm., 26:181, July 19, 1945.
_Mustela rixosa_, Svihla and Svihla, Murrelet, 13:24, January, 1932.
_Mustela rixosa rixosa_, Svihla and Svihla, Murrelet, 14:39, May, 1933.
_Type._--Male, adult, skull and skin; no. 90738, U. S. Nat. Mus., Biol. Surv. Coll.; near head of Soleduc River, 4500 ft., Olympic Mountains, Clallam County, Washington; April 28, 1897; obtained by Vernon Bailey, original no. 6213.
The skin is well prepared and in good condition. The skull (plates 5-7) is unbroken and the teeth all are present and entire.
_Range._--Olympic Peninsula, Washington, south to Olympia. See figures 25, 27 on pages 95, 149.
_Characters for ready recognition._--Differs from _M. e. anguinae_, in males, by lesser average size, hind foot ordinarily less than 33.4, and interorbital breadth ordinarily less than 8.5, in females by smaller size, total length less than 235, tail less than 65, hind foot less than 27.5, basilar length less than 30.2; from _M. e. fallenda_, in males, by length of hind foot less than 33, black tip of tail less than 36.5, weight of skull less than 1.2 grams, basilar length less than 33.5, in females length of hind foot less than 25.5, weight of skull less than 0.6 grams, basilar length less than 28.4; from _M. e. streatori_ by smaller size, in males hind foot less than 33.0, basilar length ordinarily less than 32.5, in females by hind foot ordinarily not longer than 24, by breadth of rostrum less than 8.6, depth of braincase at posterior border of upper molars less than 7.6.
_Description._--_Size._--Male: Twelve individuals of adult proportions yield average and extreme measurements as follows: Total length, 243 (205-269); length of tail, 65 (60-74); length of hind foot, 31 (29-32).
Female: Corresponding measurements of six females are: 196 (188-208), 52 (45-60?), 23.4 (22.7-24.0). An adult weighs 30 grams.
_Color._--As described in _Mustela erminea streatori_ except that least width of color of underparts averaging, in 12 males of adult proportions, 5 (0-11) per cent of greatest width of color of upper parts. Black tip of tail averaging, in same series, 26 (20-35) mm., which is 40 (31-58) per cent (average the same as in _streatori_) of length of tail-vertebrae.