Antedikwian Zoology and Botdmj, 279 



not to be passed unnoticed here ; and, although it is capable 

 of extension from later discoveries, it affords a copious illus- 

 tration of the geological position of this numerous order 

 in the English strata. These fossils existed most abundantly 

 in the chalk. One genus, Ananchites, containing many spe- 

 cies, is known only in this formation, and has not been per- 

 petuated in our present seas. 



Echini, of the genus Cidaris, first appear in the lias, but 

 unfrequently. In the lower oolite several species abound, and 

 the green sand is also rich in them. The crag contains a 

 species from this genus. Mr. Parkinson notices that one 

 genus, iSpatangus, appears first in the green sand, and then 

 in the chalk ; that it is absent in all succeeding formations, but 

 that it is found again, living in the seas of the present world. 

 Mr. Phillips, however, has observed A^patangi much lower, 

 having traced the same species in the calcareous grit, the 

 coral rag, and Kelloways rock. 



Ananchites. Galea ovata ? A group of casts in flint from chalk, Norwich. 

 TESTACEOUS MOLLU^SCA. 



Shellfish. — For convenience of arrangement, we separate 

 this division into simple univalves, simple bivalves, ancient 

 complicated bivalves, and multilocular or chambered uni- 

 valves. From the first class some naturalists have withdrawn 

 the tubular shells, to form a fifth under the head of Annulosa ; 

 and even further subdivision has been made by other classi- 

 fiers ; while, again, in another case, the whole have been 

 comprised in three classes, the Annelides, the Conchifera, 

 and Mollusca. 



