The specimens upon which the name artemisiae was based came from a narrow tongue of zonally lower country that extends northward from the range of the lighter-colored gambelii. As might be expected, topotypes are lighter in color than specimens from the north, west and east. Nevertheless, the type locality is within a geographic area that is occupied principally by a darker race, artemisiae, to the north of gambelii. The topotypes of artemisiae may be considered to be intermediate between gambelii and the darker, northern race. Thus the name artemisiae becomes available for the mice of the general area in question. The mice of the area immediately to the east of the type locality, in Washington and presumably in British Columbia and Idaho also, are essentially a mixture of the subspecies gambelii and a now mostly extinct and unnamed race that probably resembled oreas. Local variations of populations from within this area are extreme but some segregation of color and length of tail has taken place. Mice from mountainous areas resemble oreas while mice from the lowlands resemble gambelii, or, more exactly, mice from coniferous forests resemble oreas while mice from other areas resemble gambelii.
South of the area of racial mixture in northeastern Washington, in the Blue Mountains of southeastern Washington, the deer mice are like gambelii except in slightly darker color. Mice from the Blue Mountains are darker and browner than gambelii, not more reddish. There is no indication of adulteration with oreas stock. Since the Blue Mountains are a forested area and are far south of the drift border, we suppose that deer mice existed there through the last glacial period and that their dark color is an adaptation to forest habitat.
Mice similar to those of the Blue Mountains have an extensive range in Idaho ([Davis] 1939: 290). These mice have relatively uniform racial characters and constitute a "good" subspecies.
At present the deer mice of northern Washington, southeastern British Columbia, northern Idaho, northeastern Oregon, western Montana and northwestern Wyoming are called artemisiae. The mice of this extensive area are, however, of two genetic types: that type with mixed racial characters that lives in northeastern Washington and probably also farther east along the Wisconsin drift border, and that type that occurs farther south in Idaho and seems to constitute a stable subspecies.
The separation of these two types may be desirable. Detailed study of the deer mice from the area now assigned to the range of artemisiae may show that the name subarcticus (Peromyscus texanus subarcticus [Allen], 1899) is applicable to the southern form. The type with mixed racial characters must be called artemisiae. If the two types are eventually separated, the mice from the Blue Mountains of Washington will be referable to the southern form.
Neotoma cinerea.—The wood rat found over most of Washington. Neotoma c. occidentalis, probably entered the state from eastern Oregon early in the Recent and spread over most of the state. The wood rat of the Blue Mountains (alticola) probably developed from occidentalis.
A coastal race of the wood rat (fusca) occurs in western Oregon. This race, if it occurred in western Washington in pre-Vashon Time, was eliminated in Vashon Time or subsequently. In Oregon it lives in deep forests ([Bailey], 1936: 174). In Washington occidentalis occupies but a small part of the ecologic niche occupied by fusca in Oregon. Elimination of fusca from Washington through competition with occidentalis seems highly improbable. Should fusca ever cross the Columbia River and become established it would probably spread to a considerable part of western Washington.
Synaptomys borealis.—The lemming mouse seems now to be retreating northward and was an arctic species forced southward by the Vashon-Wisconsin glaciers. Unlike other alpine species, it seems to be unable to exist for long in isolated mountain areas.
Phenacomys intermedius.—The heather vole, like the lemming mouse, probably was forced southward by the Vashon-Wisconsin glaciers. In the Cascade and Rocky mountains it found suitable habitat and spread southward to almost the lower end of the Sierra Nevada in California. The Cascade race moved eastward on the Puget Bridge to the Olympic Mountains after the retreat of the Vashon ice, and northward in the Cascades. Northeastern Washington was reinvaded by the subspecies of the Rocky Mountain Fauna.
Clethrionomys gapperi and CALIFORNICUS.—The two species of red-backed mouse found in Washington were probably distinct in pre-Vashon Times. At the maximum extent of the Vashon ice, californicus was probably found in western Oregon and gapperi in the Blue Mountains, where idahoensis was developed, and in the southern Cascades (cascadensis). During or shortly after Vashon Time, gapperi crossed the Puget Bridge to become established in the Olympic Mountains. After the retreat of the ice, gapperi moved northward and eastward from the Cascades and californicus crossed to western Washington from Oregon and displaced gapperi from the lowlands.