150 



Obs. A genus, containing but a small number of species, in- 

 stituted by Sowerby under the name we have adoptod. Lamarck 

 appears not to have been aware of the previous existence of this 

 genus, when he published it under the name of Crassina in his 

 Anim. sans Vertebr. He referred it to his Nymj)hace,e& teU\naire$ ; 

 but we agree with Sowerby, in the opinion, that its proper place is 

 with his Conqites marine ; from all of which it is distinguished by 

 its cardinal teeth and interior impressions. 



Blainville in his " Manuel de Malacologie et de Conchyliologie " 

 places it as a division of his genus Venus, under the following 

 characters : 



" Solides, epaisses, suborbiculaires, subequilaterales ; deux tres- 

 grosses dents divergentes sur une valve, et deux tres-inegales sur 

 I'autre ; les impression es musculaires reunies par une ligule sans 

 sinuosite posterieure." He informs us that Defrance has announced 

 the existence of eighteen fossil species, and we described two in the 

 Journ. Acad. Nat. Sci. 



AsTARTE CASTANEA. — Specific character. Beaks nearly cen- 

 tral ; epidermis chestnut-brown. 



Venus castanea, nobis. Jour. Acad. Nat. Sci., vol. ii. p. 273. 



Ohs. It is longer in proportion to its breadth than the danmoni- 

 cnsis of Montague, and is destitute of the fine and regular striae, 

 with which the oUiquala is marked. PI. 1. 



Pandora. — Shell transversely oblong, insequilateral, inequi- 

 valve, unattached, regular, somewhat rostrated ; left valve flattened, 

 with from one to three teeth extended upon the inner surface of the 

 shell, with a fosset for the ligament ; hinge margin inflected ; right 

 valve convex, teeth one less than in the left valve, with the corres- 

 ponding fosset; ligament internal, attached to an elongated fosset 

 or cicatrice, which inclines towards the anterior margin ; miiscular 

 impressions two, distant, lateral. 



" Animal very much compressed, elongated, in the form of a 

 sheath, by the union of the edges of the mantle and its continua- 

 tion with the tubes, which are united and very short; foot small, 

 thicker before, exserted by a large slit in the mantle ; branchire 

 pointed backwards and continued into the tube." — (Blainville.) 



Ohs. The hinge teeth extend on the inner surface of the shell 

 in some degree like those of Placuna, to which genus this seems 

 to be allied, both by the position of the teeth and the perlaceous 



