304 



FOSSILS OF OXFORD CLAY. 



[Ch. XX. 



Fig 359. 



Cast of IHceras arietina. 

 Coral rag, France. 



Cidaris coronata. 

 Coral rag. 



Oxford Clay. — The coralline limestone, or "coral rag," above de- 

 scribed, and the accompanying sandy beds, called " calcareous grits" of 

 the Middle Oolite, rests on a thick bed of clay, called the Oxford clay, 

 sometimes not less than 500 feet thick. In this there are no corals, but 

 great abundance of cephalopoda of the genera Ammonite and Belemnite. 

 (Figs. 361, 362.) In some of the clay of very fine texture ammonites are 



Fig. 361. 



Belemnites hastatm. Oxford Clay. 



very perfect, although somewhat compressed, and are seen to be furnished 

 on each side of the aperture with a single horn-like projection (see fig. 

 362). These were discovered in the cuttings of the Great Western 

 Railway, near Chippenham, in 1841, and have been described by Mr. 

 Pratt* 



Fig. 362. 



Ammonites Jason, Eeinecke. Syn. A. Elizabethan, Pratt. 

 Oxford clay, Christian Malford, Wiltshire. 



* S. P. Pratt, Annals of Nat. Hist. November, 1841. 



