I.—The Skull of Protoceras

Extract

The genus Protoceras, described by the writer in 1891, from the Miocene of South Dakota, is now known to include some of the most interesting extinct mammals yet discovered. It likewise represents a distinct family, and thus deserves careful investigation and description. Before this discovery, no horned artiodactyles were known to have lived during Miocene time, and Protoceras is thus the earliest one described.