The Hemphillian McKay Reservoir, Oregon, local fauna is correlated with the Paote and Ertemte faunas of North China and Montpellier fauna of France. Study of these faunas shows an important North China-North America faunal interchange. The highest degree of interchange is among the carnivores, and the lowest in the edentates, primates, and artiodactyls. Several mammals fail to migrate successfully at this time because of the presence of ecologically equivalent mammals in the new area.
The local habitat of the major community represented at McKay Reservoir is that of a pond-bank association. Grassland and woodland elements from bordering communities are also recognized. New genera described are: Hydroscapheus, Prosomys, and Leptodontomys. New species described are: Citellus (Otospermophilus) wilsoni, Ochotona spangelei, Hypolagus oregonensis, Citellus (Citellus) mckayensis, Perognathus sargenti, Canis condoni, Felis longignathus, and Prosthennops brachirostris.