MARMOTA CALIGATA.--The absence of the hoary marmot from the Cascades of Oregon, and the presence there of _Marmota flaviventris_, indicates that the species did not occur in the southern Cascades of Washington during Vashon Time. Presumably the hoary marmot is a member of the fauna of the northern Rocky Mountains and entered the Cascades of Washington in the Recent, after which it spread widely and rapidly owing to lack of competition with any established species of marmot. MARMOTA OLYMPUS.--This species has probably lived in the Olympic Mountains since pre-Vashon Time. CITELLUS WASHINGTONI.--This ground squirrel has probably lived on the Columbian Plateau since before Wisconsin Time. CITELLUS TOWNSENDII.--The Townsend ground squirrel probably entered the Yakima Valley area from Oregon. The differences between it and its relatives in Oregon indicate a considerable period of isolation but one far shorter than the period during which _washingtoni_ is presumed to have been isolated from _townsendii_. CITELLUS COLUMBIANUS.--The Columbian ground squirrel might have been forced southward in the Rocky Mountain area by the Wisconsin glaciation, might have lived in southeastern Washington since then, and might have invaded northeastern Washington in the Recent with other species of the Rocky Mountain Fauna. CITELLUS BEECHEYI.--This ground squirrel is known to have entered Washington about 1915 from Oregon. CITELLUS SATURATUS.--The mantled ground squirrel of the Cascades probably evolved, from the _lateralis_ stock, as a separate species while isolated in the southern Cascades during Vashon Time. It is a poorly differentiated species and may actually be instead a strongly marked subspecies. CITELLUS LATERALIS.--The golden-mantled ground squirrels of northeastern and southeastern Washington are closely similar. It is deduced that _connectens_ of southeastern Washington developed the differences that characterize it while isolated, from the main stock, in the Blue Mountains area of Washington and Oregon. The race found in extreme northeastern Washington (_tescorum_) probably reached that area in relatively recent times. Its range in Washington is more restricted than that of several other members of the Rocky Mountain Fauna; areas of suitable habitat west of the Columbia River are not inhabited by these ground squirrels. Its range in Washington is almost exactly that of (_Marmota monax_). TAMIAS MINIMUS.--The least chipmunk of the Yakima Valley is the same race (_scrutator_) as that occupying the Great Basin area of Oregon and Nevada. It must have crossed the Columbia in relatively recent times. Had it been resident in the isolated Yakima Valley area for any considerable period of time, the development of distinctive racial characters there would be expected. Perhaps, then, it has not been resident there as long as has the Townsend ground squirrel which, though closely related to the ground squirrel of eastern Oregon, is racially distinct.