CYPRINA. CONCHIFERA. 99 



C. Dione, Lam. Shell somewhat heart-shaped,, transversely ribbed, 

 with a double row of spines on the anterior slope ; ribs elevated, 

 lamellar; colour purplish-red or pink. 1^ inch long. Inhabits 

 American seas. D'Argenv. pi. 21, fig. I. 



C. exoleta, Lam. Shell orbicular, white, marked with rufous lines or 

 rays, striated concentrically, and the posterior depression cordi- 

 form ; margin entire. 2 inches in diameter. Inhabits European 

 seas. B. Penn. Brit. Zool. iv. pi. 57, fig. 3. 



C. tigerina, Lam. Shell suborbicular, compressed, with decussated 

 stnre ; posterior depression minute and excavated ; margin entire ; 

 colour white ; inside pale-yellow, tinged with red round the mar- 

 gin. 1J inch long. Inhabits Indian and American seas. Rumpk. 

 Mm. pi. 42, fig. H. 



*** Internal margins crenated or dentated. 



C. pectinata, Lam. Shell ovate, variegated with white and brown- 

 ish red, with longitudinal nodulous ribs, branched at the anterior 

 end ; posterior depression oval. 1^ inch long. Inhabits Indian 

 Ocean D'Argenv. pi. 21, fig. P. 



C.flexuosa, Lam. Shell triangular heart-shaped, produced at the 

 anterior end, and marked with transverse crenated grooves, becom- 

 ing bifid towards the anterior slope ; colour whitish, reddish, or 

 frayish, more or less spotted. 1 inch long and 1} broad. Ih- 

 abits Indian seas. Rumpk. Mus. pi. 44, fig. M. 



Gen. 22. CYPRINA, Lam. Venus, Lin. 

 Shell equi valve, inequilateral, obliquely heart-shaped, with the 

 beaks bent obliquely ; three unequal primary teeth, approxi- 

 mated at their base, slightly diverging above ; a distant la- 

 teral tooth, sometimes obsolete ; ligament exterior, sunk in 

 part between the beaks. 



C. Islandica, Lam. Shell somewhat heart-shaped, ponderous, slight- 

 ly striated transversely, and the posterior depression obliterated ; 

 margin very entire ; epidermis glossy brown or blackish ; inside 



white. 3 to 5 inches long. Inhabits northern seas. B Brown's 



Illust. pi. 17, 18, fig. 11 and 19, fig. 1. 



Fossil species of this genus are found in France and Italy, and in Britain in the 

 crag and green sand. 



2. FLUVIATILE. Shell covered with a spurious epidermis and 

 with lateral teeth at the hinge. 



Gen. 23. GALATHEA, Lam. Venus, Gmel. 

 Shell equivalve, subtrigonal, covered with a greenish epidermis ; 

 primary teeth furrowed ; two in the right valve, joined at the 

 base ; three in the other, the intermediate separate and ad- 

 vancing ; lateral teeth distant ; ligament exterior. 



G. rmtofl, Lam. Shell slightly trigonal, gibbous towards the base, 

 of a milk-white colour under the greenish epidermis. 3J inches 

 long. Inhabits rivers in Geylori. An. Mus. v. pi. 28. 



