Late Pleistocene deposits in the valley of Good Creek, near the base of the Texas Panhandle, are described as a formation. An extensive vertebrate and fresh-water invertebrate fauna is listed, and the mammals are discussed in detail. The deposits are of Sangamon age, and the fauna is adapted to an interglacial climate. Sympatry of species that are now allopatric supports Hibbard's concept of interglacial climate; summers no warmer than those at present, but winters distinctly warmer. Nine species of large mammals were detected, 8 of which are extinct. Of 21 species of small mammals found, only 3 are extinct, Of the other 19, 13 live in the valley of Good Creek today, and the other 6 occur within 300 mi. Absence of the cotton rat in the Pleistocene fauna suggests that this form did not invade the southern Great Plains until after Good Creek time. Presence of the least shrew and its absence in Sangamon and earlier faunas of Kansas indicate that this species had just begun to invade the Great Plains in the Sangamon.