SIXTH JURASSIC PERIOD. 



SIXTH JURASSIC PERIOD. 



366. This stage, called the Callovian, corresponds to the 

 Oxford clay and Kelloway Rocks of the British geologists, from 

 the latter of which it takes its designation. 



367. The animal generic forms which lived in this period, 

 exclusive of the Annulata, are enumerated in the following 

 table : 



Synopsis of the Animal Kingdom (exclusive of the Annulata) during the 

 Sixth Jurassic Period. 



It appears, therefore, that of the 73 genera which existed, 

 only three were new, two of which were generic forms of Cephalo- 

 pods, called Rhychoteuthis and Paleeoteuthis. This period was 



Fig. 165. Ammonite Jason. 



remarkable for the prevalence of Ammonites, denominated Limula, 

 Athleta, Jason (fig. 165), as well as the Trigonia elongata, Plica- 

 tula peregrina, Astrea dilatata, and Terebratula Diphya. 



The Ichthyosaurus appeared for the last time in this period. 



368. The outlines of sea and land during this period under- 

 went some remarkable changes. The convulsions which ter- 



87 



