128 DIMYAIBA. 



terminating in the margin ; inside white. Two inches long. 

 Inhabits the European seas. 



Genus 24.-.CYP RIN A.— Zamarc/i. 



Generic Character. — Shell equivalve, inequilateral, obliquely 

 heart-shaped, beaks obliquely bent ; hinge with three unequal 

 teeth, approximate at the base, and slightly divergent above ; 

 lateral cardinal tooth remote, which is sometimes obsolete ; liga- 

 ment external, and partly sunk between the beaks. 



Distinguished from the genera Venus, Cytherea, and Exoleta, by having 

 one impressed lateral tooth, on the front side, which is sometimes obsolete ; 

 the nymphae or callosities of the hinge large, arched, and terminated near 

 the apices by a cavity, sometimes very deep. 



Cyprina Islandica. — The Islandic Cyprina. Plate XVI. 

 fig. 22. Suborbicular, convex, strong, irregularly striated ; cov- 

 ered with a deep black-brown epidermis ; white within. Three 

 and three-fourth inches long. Inhabits the Atlantic ocean and 

 Sritish seas. 



Genus 26.— hK^Mk.— Leach. 



Generic CAamc/er. —Equivalve, inequilateral ; hinge not quite 

 central \ umbo prominent ; hinge with two nearly obsolete pri- 

 mary teeth, lateral ones very conspicuous ; valves convex ; mar- 

 gin plain. 



Lascea rubra.— The Red LASiEA. Plate XVI. fig. 16. 

 Convex, smooth, glossy, pellucid, reddish-pink. Fourth of an 

 inch long. Inhabits the British seas. 



Section II. — Fltiviatile. 



Shells with lateral teeth at the hinge, and covered with a spu- 

 rious epidermis. 



Genus 26.— GAL ATHE A. ^Lamarck. 



Generic Character. — Equivalve, subtrigonal, covered with a 

 vitreous greenish epidermis ; two furrowed primary teeth in the 

 right valve, joined at their base ; and three in the other, the in- 

 termediate one being separate and protruding ; ligament external, 



