210 MALACOZOA. TROPIOPODA. LAMELLIBRANCHIATA. 



Family VI. — ^£enerina. 



Animal roundish or oblong, compressed, with the 

 mantle-lobes free beneath, united behind to form a tube 

 containing two siphons ; the foot compressed, extensile ; 

 two large adductor muscles. Shell varying from 

 orbicular to oblong, subcordate, convex, concentri- 

 cally striate, the umbones prominent, the hinge with 

 from two to four divergent teeth, and elongated lateral 

 teeth, the ligament external ; the frontal slope with a 

 cordate impression. Name from the Genus Venus. 



Genus 1. Lucina. — Shell suborbicular, subinequila- 

 teral; umbones small, hinge generally with two small 

 teeth in each valve ; pallial impression entire. Lucina, 

 " the goddess of child-bearing." Bruguiere. 



1. Lucina Rddula. — Shell orbicular, convex, with 

 numerous concentric narrow rugae, becoming lamelliform 

 at the two extremities. Rddula, a rasp. 



2. Lucina spinifera. — Shell elliptical-orbicular, com- 

 pressed, thin, with concentric narrow ridges, becoming 

 lamelliform at the two extremities, and at the anterior 

 especially forming spines. Spina, a prickle; fero, to 

 bear. 



3. Lucina Idctea. — Shell orbicular, equilateral, convex, 

 with numerous concentric narrow, rather irregular striae. 

 Ldcteus, milk-white. 



4. Lucina leucdma. — Shell roundish, inequilateral, 

 little convex, thin, with numerous concentric deeply im- 

 pressed striae, and faint radiating striulae. Aevnos, white 

 or shining. 



Genus 2. Cyprina. — Shell ovato-orbicular, equivalve, 

 obliquely cordiform, concentrically striate, with a per- 

 sistent lamellar epidermis, two strong divergent teeth in 

 each valve ; the ligament external ; the pallial impression 

 entire. Cyprina, a title given to Venus, from the Island 

 of Cyprus. Lamarck. 



1 . Cyprina Isldndica. — Shell obliquely cordate, round- 

 ish-ovate, thick, concentrically rugoso-striate, with the 



