Tertiary nautiloids (Eutrephoceras and Cimomia) from South Australia

Abstract

Eutrephoceras altifrons (Chapman) and E. geelongensis (Foord) from the Lower Miocene of South Australia intergrade with respect to most characters. They differ, however, in the shape of the umbilical shoulders. The two species, which occur together, are redefined, and Kummel's assignment of them to Eutrephoceras is accepted. The study of new specimens of Nautilus felix Chapman from the Upper Eocene of the Adelaide Basin indicates that this species belongs to Cimomia. Cimomia yorkensis n.sp. is described from beds of the same age.