A female from Dewey Lake, Yakima County, contained 4 embryos on September 1, 1940. One from Tye, King County, had 2 embryos on September 8, 1940. =Microtus richardsoni arvicoloides= (Rhoads) _Aulacomys arvicoloides_ Rhoads, Amer. Nat., 28:182, February, 1894. _Microtus richardsoni arvicoloides_ Bailey, N. Amer. Fauna, 17:62, June 6, 1900. _Type._--Obtained at Lake Keechelus, Kittitas County, Washington, by A. Rupert in September, 1893. Rhoads gives the altitude as 8,000 ft. This apparently is an error, for the elevation of the lake is 2,458 ft. and the summit of Snoqualmie Pass, to the west, is 3,100 ft. Probably 3,000 ft. was intended; type in Philadelphia Academy of Natural Sciences. _Racial characters._--Size large; color of upper parts dark reddish brown; underparts paler. [Illustration: 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. _Type._--Obtained in the Pashimeroi Mountains, 9,700 ft., Custer County, Idaho, by C. H. Merriam and V. Bailey in 1890; type in United States National Museum. _Racial characters._--Similar to _arvicoloides_ but slightly smaller and redder. _Measurements._--A female from Stay-a-while Spring, Columbia County, measures: total length 228; length of tail 73; hind foot 25; ear 14. _Distribution._--The Blue Mountains of southeastern Washington. =Microtus oregoni oregoni= (Bachman) Creeping mouse _Arvicola oregoni_ Bachman, Jour. Acad. Nat. Sci. Philadelphia, 8:60, 1839. _Microtus oregoni_ Miller, N. Amer. Fauna, 12:9, July 23, 1896. _Microtus morosus_ Elliot, Field Columb. Mus. Publ. 30, zoöl. ser., 1:227, February 1, 1899 (type from Boulder Lake, 5,000 ft., Clallam County, Washington). _Microtus oregoni oregoni_ Miller, U. S. Nat. Mus. Bull., 79:227, December 31, 1912. _Microtus oregoni cantwelli_ Taylor, Jour. Mamm., 1:180, August 24, 1920 (type from Glacier Basin, 5,935 ft., Mt. Rainier, Pierce County, Washington). [Illustration: FIG. 118. Distribution of the creeping mouse, _Microtus oregoni oregoni_, in Washington.]