﻿BIVALVIA. 133 



some of the smoother specimens of anceps make great approaches to it. Both cordis and 

 anceps are very abundant in the Coralline Crag. 



Cardita senilis, Lam. Crag Moll, vol. ii, p. 165, Tab. XV, fig. 1 a—f. 



Localities. Cor. Crag passim. Red Crag passim except Walton Naze. 



The shell which has hitherto gone by the name of Cardita senilis, Lam., is one of the most 

 abundant shells in the Coralline Crag, and it is found also in all parts of the Red Crag save 

 Walton, in some, if indeed not all, of which, however, it is probably only present as a deriva- 

 tive. There is some doubt whether this shell be the Venericardia senilis of Lam. or the 

 Cardita rudista of the same author, under which latter name it is figured by Homes, Tab. 

 XXXVI, fig. 2, a — d, who associates with it (and I think justly) Chama r/iomdoidea, 

 Broc, Tab. XII, fig. 16. In ' Brit. Conch.,' vol. i, p. xciii, Mr. Jeffreys says, " The Cardita 

 senilis of the same beds (Coralline Crag) is the C. sulcata of the Mediterranean," and 

 this he has repeated in the list annexed to Mr. Prestwich's Cor. Crag paper. I have, 

 however, carefully compared sulcata witli the Crag fossil and I cannot coincide in Mr. 

 Jeffreys' opinion. The recent sulcata has more rounded ribs, which are nearly smooth, 

 and not imbricated, and the ribs are united at their bases, but in senilis they are distant, 

 with a space between them. Senilis is exceedingly variable in form, as may be seen by 

 the specimens figured in ' Crag Moll.,' vol. ii, Tab. XV, fig. 1 a—f, all of which I 

 believe belong to one and the same species. As so many British authors have referred 

 to this shell for nearly half a century under the name senilis, I have not thought it 

 desirable, notwithstanding Dr. Homes' identification of it with Lamarck's rudista, to make 

 any change in the name. 



Cardium fasciatum, Mont. Crag Moll., vol. ii, p. 153, Tab. XIII, fig. 4 (as C. 



nodosum) . 



Localities. Cor. Crag passim. Red Crag passim. Chillesford bed, Aldeby. 



The shell figured in ' Crag Moll.,' under the specific name of nodosum may probably 

 be C. fasciatum, Mont. {C. elongatum, Turt.), as has been said by the author of the 

 ' Brit. Conch/ Although a very common shell in the Cor. Crag, the specimens have 

 (with very rare exceptions) the entire surface removed, and with it the tubercular orna- 

 ment, and in that state it is of very difficult determination. Mr. Crowfoot sent me 

 several small specimens from Aldeby in which parts of the exterior ornament is well 

 preserved, and these may be referred to this species. 



