Lemmiscus curtatus pauperrimus [Goldman], Proc. Biol. Soc. Washington, 54:70, July 31, 1941.
Type.—Obtained on the "Plains of the Columbia" near the Snake River, southwestern Washington by J. G. Cooper on October 9, 1860. Probably from the Bunchgrass Hills near Wallula (Old Fort Walla Walla), Walla Walla County: type in United States National Museum.
Measurements.—[Bailey] (1900: 69) gives the average of 3 adults from the vicinity of Antelope, Oregon, as: total length 115; length of tail 20; hind foot 16.
Distribution.—Known in Washington only from the type and a specimen from Badger Mountains, 8 miles southwest of Waterville ([Taylor] and [Shaw], 1929: 25).
Remarks.—This rare vole is the smallest microtine rodent in Washington. The head and body measure about 4 inches and the tail about 1 inch. The upper parts are grayish or yellowish brown and the underparts grayish. The upper incisors are not grooved and the inner and outer angles of the molars are about equal in length.
Mice of the genus Lagurus occur in Siberia and in prairie areas of the northwestern United States and Canada. The sagebrush vole inhabits the Upper Sonoran Life-zone. It prefers upland areas of low sagebrush with sparse grass. Poorly formed runways and small piles of feces indicate its presence. The type of Lagurus pauperrimus was obtained in southwestern Washington 80 years ago, and a single additional record has since been obtained. Nothing is known of its habits in Washington. The life history of related forms has been reported on by [Hall] (1928: 201-204) from Nevada and [Moore] (1943: 188-191) from Oregon.
[Davis] (1939: 326) raised the subgenus Lemmiscus Thomas (for American forms) to generic rank and [Goldman] (1941: 69) accepted this usage. Comparison of the Siberian and American species reveals but three impressive differences: the dorsal stripe of the Siberian mice, the greater development of prisms in the molars of the American species, and the presence of cement in the angles of the molars of the Siberian specimens and its lack in the American. These differences seem to be of no more than subgeneric value. [Goldman] (1941: 69) showed that all American Lagurus belong to a single species.
Ondatra zibethicus (Linnaeus)
Muskrat
Description.—The muskrat is a large aquatic rodent. Head and body measure about 14 inches; the tail about 10 inches. The body is plump and the head small. Eyes and ears are relatively small. The forefeet are small and handlike with furred wrists. The hind feet are large with webbed toes and naked wrists. The tail is narrow, constricted at the base and flattened vertically. It is scaled and possesses scattered, stiff hairs. The underfur is dense and soft. The guard hair is stiff and shiny. The upper parts are rich, dark brown. The underparts are gray washed with cinnamon.