Sciurus douglasii Bachman, Proc. Zoöl. Soc. London, p. 99, 1838.
Sciurus hudsonius Douglasii True, Proc. U. S. Nat. Mus., 7:595, 1884.
Sciurus douglasii douglasii [Miller], U. S. Nat. Mus. Bull., 128:212, April 29, 1924.
Sciurus douglasii cascadensis [Taylor] and [Shaw], Occ. Papers Chas. R. Conner Mus., no. 2:18, December, 1929.
Tamiasciurus douglasii Holdenried, Jour. Mamm., 21:406, November 14, 1940.
Type.—Obtained near the mouth of the Columbia River by David Douglas.
Measurements.—Fifteen males and 10 females from the lowlands of western Washington average, respectively: total length 317, 320; length of tail 121, 126.7; hind foot 50, 49.4; ear 23.2, 22.6; weight 204, 202 grams.
Distribution.—From the eastern base of the Cascade Mountains westward to the Pacific. Marginal occurrences are: Nooksack River ([Taylor] and [Shaw], 1929: 18), Lake Wenatchee (W. W. D.) and Wenatchee ([Taylor] and [Shaw], 1929: 18).
Remarks.—Squirrels from the Puget Sound area are slightly less intensely colored than specimens from the ocean coast and the Olympic Mountains. Those from the higher and eastern Cascade Mountains are paler still. When, however, squirrels from the Cascades of Washington are compared with individuals of the race inhabiting the Cascades of Oregon, it is apparent that the Washington squirrels are nearest to douglasii. The pale tips of the hairs in the tail of the Oregon race are strikingly white while in Washington specimens they are orange or yellow.
The Douglas squirrel resembles the red squirrel in size and proportions but differs in being dusky olive (less reddish) on the upper parts and orange instead of white on the underparts.