Microsyopsinae and Hyopsodontidae in the Sespe Upper Eocene, California

Occurring in association with the recently described tarsiid,(1) Dyseolemur pacificus, in the Eocene deposits, north of the Simi Valley, California, is a new genus of the subfamily Microsyopsine and a new species of the genus Hyopsodus. Aside from the interest inherent in the new types, the presence of these forms gives added reason for regarding the faunal assemblages now being uncovered at locality 180 and stratigraphically related localities in the Sespe as definitely older than that known from locality 150. Moreover, these types suggest again a post-Bridger and an upper Eocene age for this stage in the succession of faunal horizons of the Sespe.