The new genus and species Eobelemnites caneyense is described from a specimen from a boulder, evidently Mississippian in age, from the Johns Valley (Caney) shale of Oklahoma. Preservation of this form is such as to permit a close study of the phragmocone, bringing out for the first time the presence of such structures as the septal furrow and cameral deposits in belemnoids. These features persist into much higher forms. Comparison with other belemnoids is made difficult owing to uncertainty as to the relative values of the several classifications proposed, and owing to uncertainties as to structural features of some crucial Mesozoic species. However, Eobelemnites appears to unite the Protobelemnitidae and Eubelemnitidae if the criteria of these groups are valid. The genus shows no features which present a clue to the precise origin of the Coleoidea, but it indicates that the coleoids were differentiated much earlier than was previously believed.