21^ 



tendency towards the depressed spiral form in this shell, evinced 

 by the ^great obliquity of the cardinal portion, which hardly pro- 

 trudes beyond the margin, would arrange it with the genus Gry- 

 phsea in the estimation of some authors ; a group, however, which 

 we consider as a mere subdivision of the present genus. On the 

 lower part of the plate is represented one of many specimens 

 which I obtained in Florida attached to various objects. It seems 

 to be closely related to a fossil of Virginia, to which Mr. Conrad 

 has given the name 0. solea, but as my specimen of that shell is 

 imperfect and I have not his description, \ cannot determine the 

 degree of affinity ; it may possibly be a variety of that species. 

 I have also a specimen from the Antilles, and another that is re- 

 versed. Plate 58. 



Cytherea. — Shell bivalve, equivalve, inequilateral, suborbicu- 

 lar, trigonate or transverse ; four cardinal teeth on one valve, three 

 of which diverge from the summit and one is isolated, situated 

 under the lunule; three divergent cardinal teeth upon the other 

 valve, and a fosset at a little distance, parallel to the lunule mar- 

 gin ; no lateral teeth. 



Ohs. A genus of beautiful marine shells, included by Linnc in 

 the genus Venus, but separated by Lamarck in consequence of the 

 middle tooth of the hinge being profoundly divided into two, and 

 the posterior tooth being distant and parallel to the lunule edg'e. 

 The name of Meretrix, which that author first applied to this genus, 

 he subsequently thought proper to reject in favor of the present 

 designation. An allied genus, the Astarte of Sowerby (^Crassma, 

 Lam.), has but two teeth in each valve. Cijdas, Cyrena and 

 Megadesma have remote lateral teeth ; Cyprhia has one remote 

 lateral tooth, and the posterior muscular impression of Lucina is 

 elongated. 



The species are numerous, inhabitants of almost every shore, 

 and are imbedded in many fossil localities. The Japanese and 

 Chinese paint and gild the inner side of C. lusoria with vari- 

 ous devices, and make use of it in their games of chance, whence 

 its name. 



Cytherea albaria. — Desc. Shell transversely oblong-ovate, 

 nequilateral, wrinkles of growth more obvious towards the margin, 

 omewhat polished, with a slight appearance of rather broad, nu- 



