_Type._--Obtained at The Potholes, 10 miles south of Moses Lake, Grant County, Washington, by W. W. Dalquest on March 24, 1940; type in Museum of Vertebrate Zoölogy. _Racial characters._--Large size; dark blackish color; long fur; wide, angular skull. _Measurements._--Six male and 12 female topotypes average, respectively: total length 176.6, 168.0; length of tail 45.1, 43.8; hind foot 20.8, 20.3; ear 14.0, 13.4. _Distribution._--The Columbian Plateau, in the Grand Coulee area. =Microtus montanus= (Peale) Montane meadow mouse _Description._--Montane meadow mice have short tails, flaring zygomatic arches, and heavily ridged skulls. They are small, about 6-1/2 inches long, and buffy-gray in color. Their short tails, less than one-third the length of head and body, and gray color separate them from all other Washington meadow mice. Montane meadow mice are widely distributed in the southwestern United States, where numerous races are found. They occupy damp meadows and marshes in the arid subdivision of the Transition Life-zone of eastern Washington. They seem to require deep, dense cover of grasses, reeds, or sedges, near water. They are usually associated with harvest mice (_Reithrodontomys megalotis_), wandering shrews (_Sorex vagrans monticola_), and muskrats (_Ondatra zibethica_). Hawks and owls are their principal enemies, but predatory mammals and snakes probably kill many. Montane meadow mice evidently are both diurnal and nocturnal; specimens were taken in the daytime as well as at night, and captives were active periodically day and night. Captives were extremely quick in their movements. If disturbed they sat up on their haunches and chattered indignantly. It was almost impossible to handle them without being bitten. The trails of montane meadow mice are narrower than those of other meadow mice, and appear to be used the year around. Burrows are numerous where the mice are plentiful. A heap of damp earth marks the entrance to each burrow. One nest of _M. m. canescens_ near Lake Chelan, Chelan County, was under a log on a small knoll in a marsh. The nest was round, about 8 inches in diameter, and was composed of cattails, grasses, and moss. [Illustration: FIG. 114. Distribution of the montane and Townsend meadow mice in Washington. A. _Microtus montanus nanus._ B. _Microtus montanus canescens._ C. _Microtus townsendii townsendii._ D. _Microtus townsendii pugeti._] _Microtus montanus nanus_ (Merriam) _Arvicola (Mynomes) nanus_ Merriam, N. Amer. Fauna, 5:63, July 30, 1891. _Microtus nanus_ Miller, Proc. Biol. Soc. Washington, 11:67, April 21, 1897. _Microtus nanus nanus_ Miller, Bull. U. S. Nat. Mus., 128:409, April 29, 1924. _Microtus montanus nanus_ Hall, Proc. Biol. Soc. Washington, 51:133, August 23, 1938.