Long-tailed meadow mice are widely distributed over the western United States, Canada, and Alaska. In Washington the long-tailed meadow mouse has been taken in many habitats. One specimen was taken along a small, temporary stream through sagebrush in the Upper Sonoran Life-zone. Others were found in marshes and near water in the arid subdivision of the Transition Life-zone. In the humid subdivision of the Transition Life-zone they are not uncommon in damp areas along the ocean coast, but are rather rare in dry, grassy habitats. In the Canadian and Hudsonian life-zones they are fairly common in forest-free, grassy places, being most abundant near talus slides. Altitudinally they range from sea level to 6,000 feet. Long-tailed meadow mice are rather rare. Several were taken in the daytime at Round Top Mountain, Pend Oreille County, and two others were taken in daytime two miles south of Tenino, Thurston County. However most of the specimens were caught at night. Long-tailed meadow mice do not, at least ordinarily, make trails as do other meadow mice. Specimens are usually taken unexpectedly, and intensive trapping in the area where a specimen or two is taken rarely yields additional individuals. Two specimens taken in the Cascade Mountains in September were pregnant; one contained two embryos and the other four. =Microtus longicaudus halli= Ellerman _Microtus mordax angustus_ Hall, Univ. California Publ. Zoöl., 37:13, April 10, 1931 (not of Thomas, 1908). _Microtus longicaudus angustus_ Goldman, Jour. Mamm., 19:491, November 14, 1938. _Microtus mordax halli_ Ellerman, Fam. and Genera of Living Rodents, British Mus. Nat. Hist., 2:603, March 21, 1941 (new name for _Microtus mordax angustus_ Hall). _Type._--Obtained at Godman Springs, 5,700 ft., Blue Mountains, Columbia County, Washington, by S. H. Lyman, on September 1, 1927; type in Museum of Vertebrate Zoölogy. _Racial characters._--Size small; color of sides pale grayish brown; brown dorsal stripe conspicuous; tail relatively short. _Measurements._--Four males and 5 females from eastern Washington average, respectively: total length 164.8, 166.6; length of tail 55.8, 55.8; hind foot 22.0, 21.4. _Distribution._--From the Blue Mountains of southeastern Washington north, along the eastern edge of the state, to British Columbia, and thence west, north of the Columbia River, to the Cascades, and south along the eastern edge of the Cascades to the Wenatchee Mountains. Marginal occurrences are: Pasayten River (Taylor and Shaw, 1929: 24), Hart Lake (Taylor and Shaw, 1929: 24), Blewett Pass (W.W.D.), Boulder Cave (W.W.D.), and Satus Pass (W.W.D.).