40 Dr. J. E. Gray on some Families of Bivalve Shells. 



M. Deshayes shortly afterwards (Mag. Zool. 1835, t. 70) de- 

 scribed the auimal, and observed that he had previously suggested 

 for the genus the name Cyrenella, and proposed to place it be- 

 tween the genera Lucina and Venus, which M. Joannis combats 

 in the same paper. 



1. Cyrenoida Dupontia, Joannis, Mag. Zool. 1835, t. 6. 



Hal). River of Senegal. 



Is the only species known; the new species referred to this 

 genus by Mr. Adams (Proc. Zool. Soc. 1849) and M. Deshayes 

 being species of Sphcerella of Conrad belonging to the family 

 Lucinidte. 



Fam. 7. Cardiad^, Gray, Syn. B,M. 1810, 137; 1842, 75. 



Cardinal teeth 2 * 2, placed so as to form a cross when the 

 valves are closed ; lateral teeth lamellar, elongate. Shell costate. 

 Periostraca thin, rarely distinct. Siphonal inflection none. Si- 

 phons very short, separate. 



A. Shell gaping and fumislied with a serrated posterior margin. 



1. Cardium, Gray, P. Z. S. 1847, n. 557. Shell subglobose, 

 hinder gape distinct. 



* Gape very large. C. indicum. ** Gape moderate. C. cos- 

 tatum. 



2. Bucardium. Shell subglobose, costated, hinder gape nar- 

 row and strongly toothed on the hinder edge. 



* Shell as long as high, costated. B. ringcns. ** Shell higher 

 than long. B. p7-ocerum. *** Shell, hinder slope subcarinated. 



B. unedo. 



3. Papyridea, Swainson, Gray, P. Z. S. 1847, n. 560. Shell 

 oblong, elongate ; hinder gape moderate, toothed. P. soleniforme. 



4. Fulvia. Shell subglobose, rather produced behind ; hinder 

 gape moderate, slightly toothed. F. apet-ta. 



B. Shell closed and smooth, or nearly smooth behind. 



5. Cerastes, Poli. Cardium, part.. Gray, I. c. n. 557. Shell 

 subcordate, convex behind ; lunule simple ; cardinal teeth well 

 developed. 



* Rounded, ribbed. C. aculeatum. ** Rounded, smooth. C. 

 norvegicum. *** Rounded, anterior half obliquely ribbed. 



C. {Eoliciim. **** Subcarinate. C. medium. ***** Costate, 

 hinder slope keeled. C. hemicardium. ****** Smooth, hinder 

 slope keeled [Didacna). C. lineatum. 



6. Aphrodita, Lea, Gray, P. Z. S. 1847, n. 557. Shell sub- 

 cordate ; lunule simple; cardinal teeth rudimentary. A. eden- 

 tula. 



