50 SECOND SUPPLEMENT TO THE CRAG MOLLUSCA. 



list in Mr. Prestwich's paper, in which the name was introduced from the specimen of 

 cylindrica now under consideration. Pholas lata is also given in the same memoir as 

 from Beaumont, but I do not know such a species unless it be Pholas crispata, to 

 which shell the name of lata was given by Lister (see the synonyms of that shell in vol. ii 

 of ' Crag. Moll.,' p. 296). 



Venus dysera, Brocchi, and Venus fasciala, Dacosta, are given by Mr. A. Bell 

 from the Cor. Crag, but I believe the former of these to be the young state of Venus 

 imbricata, a specimen of which I had represented in 'Crag Moll.,' vol. ii, Tab. XIX, 

 fig. 3 b. This may possibly be, in the young condition, undistinguishable from 

 V.fasciata, but I have not yet seen any specimen from the Cor. Crag that could be 

 pronounced positively as identical with that species. The young of many proximate but 

 distinct species so closely resemble each other as to be incapable, in that state, of separa- 

 tion, the specific distinction ouly appearing as the animal advances in growth. I cannot 

 therefore admit dysera into my list at all, nor fasciala into it as a Cor. Crag shell. 



