Previous to Vashon-Wisconsin Times, pocket gophers occupied at least the Cascade Mountains and the Columbian Plateau of Washington. The race occupying the Columbian Plateau, _devexus_, was probably racially distinct in pre-Wisconsin time. The descent of the Vashon-Wisconsin glaciers isolated gophers in the southern Cascades. Three racial stocks developed there: _shawi_ in the Mount Rainier area; _limosus_ in the Columbia River Valley south of the Cascades; and _immunis_ in the mountainous area between the other two races. At the maximum extent of the Wisconsin ice, gophers from the Columbia River Valley (_limosus_) were able to cross the Simcoe Bridge and reach the Blue Mountains. With the retreat of the Wisconsin ice, the Simcoe Bridge was closed. Gophers isolated in the Blue Mountains developed the racial characters of _acqualidens_ and those between the Blue Mountains and the Columbia River intergraded with the desert race, _devexus_. These intergrades, which have, also, some characters of their own, bear the name _columbianus_. Gophers in the southern Cascades (_limosus_) moved westward on prairie-like river terraces to Clark County where, isolated, they became racially distinct (_douglasii_). Gophers from the Mount Rainier area (_shawi_) moved westward on glacial outwash trains to the extensive outwash aprons of the Vashon glaciers in the area about Puget Sound. Here they multiplied and spread to the Olympic Mountains. Growth of forest on the original outwash apron broke the area into numerous isolated prairies. Gophers in the Olympic Mountains (_melanops_) were isolated from those in the area about Puget Sound. Six distinct races originated on the isolated prairie (_glacialis_, _tacomensis_, _pugetensis_, _yelmensis_, _tumuli_, _couchi_). Following the retreat of the glacial ice from eastern Washington, pocket gophers from the Blue Mountains of Oregon (_wallowa_) moved northward into Washington and gophers from the Rocky Mountain Fauna of Idaho moved onto the deglaciated part of northeastern Washington. From northeastern Washington they spread westward to the Cascades and thence southward to meet the native gophers of the Cascades in the Yakima Valley Area. No racial differentiation in these gophers occurred; all are referable to _fuscus_. Where _fuscus_ and the native gophers came together in the Yakima Valley, a new race, _yakimensis_, developed. PEROGNATHUS PARVUS.--Three races of the pocket mouse occur in Washington. Two of these (_lordi_ and _columbianus_) occur on the Columbian Plateau. Like many desert species that occur on the Columbian Plateau, the pocket mice are rather different than their relatives in eastern Oregon. Presumably they have been isolated on the plateau since before Vashon-Wisconsin Times.