3. Rocky Mountain Fauna. If this fauna be thought of as including mammals of the Rocky Mountains of the United States, and also those of the subarctic faunal area to the east of these mountains in Canada, the species in Washington are as follows:
| Sorex palustris | Synaptomys borealis | |
| Microsorex hoyi | Phenacomys intermedius | |
| Lynx canadensis | Clethrionomys gapperi | |
| Marmota caligata | Microtus richardsoni | |
| Citellus lateralis | Ochotona princeps | |
| Citellus columbianus | Lepus americanus | |
| Tamias amoenus | Rangifer montanus | |
| Tamiasciurus hudsonicus | Oreamnos americanus | |
| Glaucomys sabrinus |
Of the three, the Great Basin Fauna is the most distinct. Only about twenty species which occur within the Great Basin Faunal Area, occur also outside of it in one or both of the two other faunal areas. Most of these twenty are subspecifically different in the Great Basin Faunal Area as contrasted with one or both of the other areas. Each of the other two areas has no less than 32 species that are not restricted to it.
SPECULATION AS TO EMIGRATIONAL
HISTORY OF THE MAMMALS
The present fauna of the state of Washington was derived in part from Asia and in part from native forms. Great changes occurred in early Pleistocene through emigration. By the late Pleistocene most of the mammals now occurring in the state of Washington were as they are today. The greatest changes that seem to have occurred in the late Pleistocene are the extinctions of numerous groups, locally or totally. Among the carnivores, [Matthew] (1902: 321) reports remains of the great lion, Felis atrox, associated with such familiar species as the badger, cougar, lynx and mountain goat. The great lion was very similar to the modern African lion but was fully a fourth larger. Associated with the great lion in the California tar pits are the carnivorous short-faced bears (Tremarctotherium), as large as the Alaskan brown bears; dire wolves (Aenocyon), larger than timber wolves; and saber-tooth tigers (Smilodon). These forms were probably also present in Washington in the late Pleistocene. [Matthew] (loc. cit.) reports remains of the giant beaver, Castoroides, from the Silver Lake deposit of Oregon. This great beaver, as large as a black bear, was doubtless a resident of Washington also. Peccaries, camels, bison, horses and giant ground sloths have been recorded from Pleistocene deposits of Washington and nearby areas. Of the elephant tribe, the mastodon and several species of mammoths were present.
These extinct forms have doubtless exerted some influence on the past distribution of mammals in Washington and possibly have had an effect on the distribution of members of the living fauna. One species of the mammoth, at least, existed in Washington in postglacial time. Remains of this form, Elephas columbi, have been found in Vashon till.
The three faunas of Washington can be placed in two categories. One is Sonoran, essentially a desert type, and occupies the Columbian Plateau. The other two are forest faunas, predominantly boreal in complexion, and are closely related. The Rocky Mountain Fauna is found in the Blue Mountains and in northeastern Washington. The Pacific Coastal Fauna is found in western Washington.