With the advance of the Vashon ice, mammals north of the ice border were all or mostly eliminated. Climatic conditions south of the border of the ice probably were strongly affected by it. Remains of mammoths have been found in Vashon till. The presence of many non-boreal species of mammals in southwestern Washington indicates their persistence there and that conditions therefore were not intolerable for them. Probably the climate of southwestern Washington was cool and dry. Fir, spruce, and Douglas fir may have been the dominant trees. Hansen (1941 A: 209) found evidence from studies of pollen that coniferous forests were growing in west-central Oregon in late glacial time. These pollen studies of postglacial peat bogs by Henry P. Hansen give evidence of postglacial climatic changes. Hansen points out (1941 B, 1941 C) that climatic changes west of the Cascades were probably slight because of the influence of the Pacific Ocean. Pollen profiles indicate an early, cool, dry climate followed by a warmer one and increasing humidity. The present climate may be considered cool and humid. Most of western Washington lies in the Humid subdivision of the Transition Life-zone. [Illustration: FIG. 18. McDowell Lake, Little Pend Oreille Wildlife Refuge, Stevens County, Washington, September 29, 1939. (Fish and Wildlife Service photo by Victor B. Scheffer, No. 730.)] The pre-Wisconsin climate of eastern Washington is unknown. From the loessial nature of the Palouse Soil (Bryan, 1927), a preglacial deposit, the area would seem to have been arid, probably a grassland or a sagebrush desert. If the fossil fauna discovered at Washtuckna Lake, Adams County, is of this period, the forest conditions of the Blue Mountains were slightly more extensive than at present. The glacial climate of the Columbian Plateau in Wisconsin time was probably cool and arid. Pollen studies by Hansen (1939, 1940) indicate increasing dryness and warmth since the retreat of the Wisconsin ice. Present-day climate on the Columbian Plateau is warm and dry. The plateau is principally a sagebrush desert. The glaciated area to the north is cooler and more humid, supporting extensive forests of yellow pine and other conifers. THE FAUNAS We have mentioned elsewhere that three different mammalian faunas occur in Washington. These may be described as follows. 1. THE GREAT BASIN FAUNA. This fauna is best typified by such genera as _Perognathus_ and _Dipodomys_. Species that, at least in Washington, are confined to this fauna are: