_Remarks._--The good series of beaver skulls available from several areas of Washington has led to careful comparison of Washington material with specimens from Vancouver Island. Skulls from extreme southwestern Washington are small and decidedly short, being referable to the race _idoneus_. No satisfactory way of distinguishing between the others could be found and all are consequently referred to the earliest named form, _leucodonta_. =Castor canadensis idoneus= Jewett and Hall _Castor canadensis idoneus_ Jewett and Hall, Jour. Mamm., 21:87, February 15, 1940. _Type._--Obtained at Foley Creek, tributary to Nehalem River, Tillamook County, Oregon, by C. Leach on December 15, 1914; type in California Museum of Vertebrate Zoölogy. _Description._--Similar to _leucodonta_ but smaller, darker, with shorter and wider skull. _Distribution._--Lowlands near the mouth of the Columbia River. Specimens from Puget Island (U. S. N. M.) have been examined. =Onychomys leucogaster fuscogriseus= Anthony Northern grasshopper mouse _Onychomys leucogaster fuscogriseus_ Anthony, Bull. Amer. Mus. Nat. Hist., 32: 11, March 7, 1913. _Type._--Obtained at Ironside, Malheur County, Oregon, by H. E. Anthony, in 1912; type in American Museum of Natural History. _Measurements._--Nine males and 5 females from Franklin, Benton, and Walla Walla counties, Washington, average, respectively: total length 132.3, 133.0; length of tail 35.8, 35.6; hind foot 19.2, 19.6; ear 17.6, 17.6; weight 23.3, 24.1 grams. _Distribution._--The Columbian Plateau, southeastern Washington, and the Yakima Valley, ranging north to Douglas (Taylor and Shaw, 1929: 21), west to Yakima (M. V. Z.), east to Asotin (Taylor and Shaw, 1929: 21) and south to Wallula (Taylor and Shaw, 1929: 21). [Illustration: FIG. 104. Distribution of the northern grasshopper mouse, _Onychomys leucogaster fuscogriseus_, in Washington.] _Description._--A mature grasshopper mouse is slightly larger than a house mouse; the head and body measure about 4 inches and the tail about 1-1/4 inches; it may be recognized by the rather plump body, naked ears, short, thick and tapering tail and soft, dense fur. The upper parts of adults are buffy. Younger animals are blue-gray above. Underparts and tail are white.