The Cretaceous ammonite genera Discohoplites Spath and Hyphoplites Spath

The discovery in the uppermost Albian of the Dorset coast of some new species of two genera of ammonites belonging to the last of the hoplitid stock led to re-examination, and redescription where necessary, of all the species of the two genera, Discohoplites Spath and HyphopUtes Spath. In all, five new species and four new chronological subspecies and varieties are described. The Cenomanian species of Hyphoplites , which have nowhere been methodically described, are dealt with in detail and figured. With the knowledge of the new forms it has proved possible to trace with reasonable certainty the Albian ancestors of the well-known Cenomanian species falcatus and curvatus and their allies. The phylogeny of the two genera is discussed in detail.