Zapus trinotatus [Rhoads], Proc. Acad. Nat. Sci. Philadelphia, 1894, p. 421, January 15, 1895.
Zapus imperator [Elliot], Field Columb. Mus. Publ. 30, zoöl. ser., 1:228, February 1, 1899 (type from Sieg's Ranch, Elwha River, Olympic Mountains, Clallam County, Washington).
Type.—Obtained on Lulu Island, mouth of Fraser River, British Columbia, by S. N. [Rhoads] on May 31, 1892; type in Philadelphia Academy of Natural Sciences.
Racial characters.—Similar to oregonus but brighter; sides orange; underparts creamy white; buffy area often present on chest.
Measurements.—Twenty males and 15 females from western Washington average, respectively: total length 230, 233; length of tail 140, 140; hind foot 33, 32.8; ear 14.9, 16.3; weight 23.7, 25.7 grams.
Distribution.—Western Washington and the Cascade Mountains, east in the northern Cascades at least to Tomyhoi Lake (W.W.D.).
Remarks.—Actual intergrades between trinotatus and kootenayensis have not been examined but the differences separating the two forms are of the degree that usually distinguish subspecies. Since trinotatus occurs in the high Cascades as far east as Mount Baker, at least, and kootenayensis probably occurs in the northeastern Cascades, the two forms doubtless come together in the rugged, inaccessible area between these two localities. Further collecting will probably show a narrow zone of intergradation in extreme western Okanogan County.
