90 CLASS I. TROPIOPODA. ORDER I. B1MUSCULOSA. 



CYPRINA, Lamarck. 



Testa sequivalvis, inrequilateralis, oblique cordata, umbonibus oblique 

 curvis ; epidermide fusca induta. Dentes cardinales tres, ad basem 

 appropinquantes, superne divaricati. Dens lateralis posticus, a car- 

 dine remotus. Ligamentum externum, in sinu marginali parti m 

 immersum. 



This genus may be said to partake of the characters of Oyrena and 

 Venus, thus serving to establish a close affinity between the fluviatile 

 and marine Conchacea. It has comparatively a large shell, which may 

 be easily recognised by its thick fibrous epidermis. 



The shell of Cypriua is described as equivalve, inequilateral, obliquely 

 cordate, with the umbones obliquely curved. There are three unequal car- 

 dinal teeth, approximating at the base, and diverging a little superiorly ; 

 and there is a posterior lateral tooth at some distance from the hinge. 

 The ligament is external, partly buried in a deep marginal sinus. The 

 Cyprinee mostly inhabit the North Se;is. 



Example. 



PI. LXV. Fig. 1 and 2. 



Cyprina vulgaris, Sowerby, Genera of Shells, No. 32. Enc, Meth., 



pi. 301. f. 1. 

 Venus Islandica, Linnseus. 

 Cyprina Islandica, Lamarck. 



ASTARTE, Sowerby. 



Testa suborbiculata, plerumque transversa, eequivalvis, inaequilateralis, 

 epidermide fusca induta. Cardo dentibus duobus, validis, divari- 



