Racial characters.—Size large; color of upper parts dark reddish brown; underparts paler.
Fig. 117. Distribution of the water rat in Washington. A. Microtus richardsoni arvicoloides. B. Microtus richardsoni macropus.
Measurements.—A female from Tomyhoi Lake, Whatcom County, measured: total length 242; length of tail 68; hind foot 27; ear 17. A female from Tye, King County, measured: 257; 83; 26; 17.
Distribution.—The Cascade Mountains, from Tomyhoi Lake (W.W.D.) south to Potato Hill ([Taylor] and [Shaw], 1929: 25).
Microtus richardsoni macropus ([Merriam])
Arvicola (Mynomes) macropus [Merriam], N. Amer. Fauna, 5:60, July 30, 1891.
Microtus richardsoni macropus [Bailey], N. Amer. Fauna, 17:61, June 6, 1900.
Microtus richardsonii macropus [Taylor] and [Shaw], Occ. Pap. Chas. R. Conner Mus., no. 2:25, December, 1929.