﻿SUPPLEMENT TO THE BIVALVIA. 



9 



side. 1 This latter specimen very closely resembles the small variety of the Crag and 

 Post-glacial species, C. fluminalis, the only difference between them that I can detect 

 being the greater length of the lateral teeth in fluminalis, and in the ridges or imbrications 

 present on that species, the exterior of the Eocene shell being smooth. As, however, the 

 ridges which are so strong on recent specimens of fluminalis become more or less obscure 

 in the fossil, it is possible that the Eocene species, trigona, may not in life have been 

 so destitute of imbrications as the specimens preserved fossil appear to be. C. trigona 

 also closely resembles C. pisum, and is not far removed from C. brevittscida, Desh, ' An. 

 sans Vert, du Bas. de Paris,' PI. 36, figs. 9 — 11 ; but this latter shell is more transverse. 



10. Cyrena anceps, S. Wood. Tab. A, fig. 12. 



Length, 1 inch. 



Locality. Dulwich {Meyer). 



This represents another specimen sent to me by Mr. C. Meyer, and on the label was 

 written, " Cyrena, a doubtful form," and said to come from the leaf clay at Dulwich. 

 Its peculiarity seemed to me deserving of a special representation, and I have assigned it 

 the above specific name, although it may only be a distorted specimen of cuneiformis, or 

 of another of the common species from the same locality. 



11. Cyrena tumida, S. Wood. Tab. A, fig. 7 a, b. 



Length, lfths of an inch. 

 Locality. Dulwich (C. Evans). 



This is another doubtful form. It somewhat resembles in outline C. cuneiformis, 

 but I have never seen a specimen of that species inflated like the present one. The 

 one figured is the only specimen that I have seen, and I have provisionally, therefore, 

 assigned it as a new species under the above name. The two valves were so closely 

 cemented together by its stony matrix that I have been unable to see the interior. It 

 is from the cabinet of Mr. C. Evans. 



1 These two characters have not been sufficiently represented by the artist in fig. 9 a, b. 



B 



