Ch. XX.] 



Fig. 354 



COEALS OF THE OOLITE. 

 Corals of the Coral Rag. 



303 



Fig. 355. 



Thecosmilia annularis, Milne Edw. and J. Hainan. 

 Coral rag, Steeple Ashton. 



Thamnastrma. 

 Coral rag, Steeple Ashton. 



again recur in Yorkshire, near Scarborough. The Ostrea gregarea (fig. 356) 

 is very characteristic of the formation in England and on the continent. 



One of the limestones of the Jura, referred to the age of the English 

 coral rag, has been called " Nerinaean limestone" (Calcaire a Nerinees) 

 by M. Thirria ; Nerinoea being an extinct genus of univalve shells, much 

 resembling the Cerithium in external form. The annexed section (fig. 357) 

 shows the curious form of the hollow part of each whorl, and also the 

 perforation which passes up the middle of the columella. N. Goodhallii 



Fig. 857. 



Fig. 356. 



Fig. 353. 



Ostrea gregarea. 

 Coral rag, Steeple Ashton. 



JiTerinma hieroglyphica. 

 Coral rag. 



Nerinma Goodhallii, Fitton. 

 Coral rag, Weymouth. \ nat. size. 



(fig. 358) is another English species of the same genus, from a formation 

 which seems to form a passage from the Kimmeridge clay to the coral 

 rag* 



A division of the oolite in the Alps, regarded by most geologists as 

 coeval with the English coral rag, has been often named " Calcaire a Di- 

 cerates," or " Diceras limestone," from its containing abundantly a bivalve 

 shell (see fig. 359) of a genus allied to the Chama. 



* Fitton, Geol. Trans., Second Series, vol. iv. pi. 23, fig. 12. 



