Article: Perisphinctid ammonites of the Upper Calcareous Grit (Upper Oxfordian) of North Yorkshire
Twenty-three species of perisphinctid ammonite, belonging to the genera Perisphinctes, Decipia and Microbiplices, are described from the lowest Upper Oxfordian Upper Calcareous Grit Formation of North Yorkshire. A new species, Decipia ravenswykensis, is described, and Pseudopomerania is proposed as a new subgenus of Perisphinctes, to include some until now little understood perisphinctids previously assigned to Decipia. A comparison is made with successions of the same age elsewhere in Britain and in continental Europe. Revised correlations are proposed with the standard successions in the Wash area of England and in the French Jura.