_Evotomys pygmaeus_ Rhoads, Proc. Acad. Nat. Sci. Philadelphia, p. 284, October 23, 1894 (type from mouth of Nisqually River, Pierce County, Washington). _Evotomys gapperi occidentalis_ Taylor and Shaw, Occ. Papers Chas. R. Conner Mus., no. 2:23, 1929. _Clethrionomys occidentalis_ Hall, Murrelet, 13:79, September, 1932. _Type._--Obtained at Aberdeen, Grays Harbor County, Washington, by T. S. Palmer, on August 16, 1889; type in United States National Museum. _Measurements._--Ten males and 10 females average: total length 137; length of tail 45; hind foot 18; ear 12.3. _Distribution._--The lowlands of western Washington, east at least to Cottage Lake (W. W. D.). _Remarks._--Specimens from the type locality of _occidentalis_ and other places along the ocean coast are larger and brighter in color than specimens from farther inland, but the difference appears to me to be insufficient to warrant subspecific separation of the two lots. _Clethrionomys californicus_ resembles _Clethrionomys gapperi_ but is darker and duller in color with the red dorsal area more obscured and forming less of a stripe. _C. californicus_ is found in the forested lowlands of western Washington, Oregon, and northern California, and in the Cascades of Oregon. In Washington, it is confined entirely to the forest where it is trapped under logs and on the layer of dead needles at the bases of conifers. Mice of this species were numerous in the forest along the Pacific Coast on the Long Beach Peninsula and at Aberdeen, Grays Harbor County. At Lost Lake Prairie, Mason County, at the southeastern base of the Olympic Mountains, they were rather scarce, but were the only mammals taken in the deep woods. Near Shelton, Mason County, at the eastern edge of the Olympic Mountains, a number of specimens were taken along with twice as many _Peromyscus maniculatus_. At Cottage Lake, King County, near Seattle, they were rare, comprising about two per cent of the mammals taken in two weeks' trapping. Almost nothing was learned of the habits of these mice. They seem to be rigidly restricted to a habitat where few plants other than trees grow. The stomachs examined contained pasty masses of finely chewed white vegetation with occasional gray particles that might have been bits of lichens. The mice do not make runways like those of _Microtus_. =Microtus pennsylvanicus= (Ord) Pennsylvanian meadow mouse _Description._--The upper parts are dark blackish brown and the underparts grayish or whitish. The tail comprises about a fourth of the total length and the foot does not exceed 21 mm. These two features separate it from most other species of meadow mice. From _Microtus oregoni_ it may be separated by its larger size, blackish color and well-developed eyes. From _Microtus montanus_ it differs in being larger, darker, and in having a closed posterior loop on the innerside of the second upper molar.