176 COSCUYUA^DITHYRA. 40. 



Shell oval- triangular or oblong, equivalve, inequilateral, closed ; 

 with tiie beaks close together. Hinge with an oblique project- 

 ing spoon-shaped tooth in each valve: lateral teeth on each 

 side numerous, sharp-pointed, inclining outwards, and alter- 

 nately closing together. Ligament internal. 



Except in its numerous teeth, this genus has nothing in com- 

 mon with the Area and the Pectunculus. The primary tooth 

 consists of an oblique hollow projecting inwards horizontally, 

 in which the ligament is fixed : and the lateral ones of slender 

 sharp teeth, like the pectinations of a comb, the middle ones 

 longer. 



^'? Margine interno crennlato. I. 

 The inner margin finely notched. 



Nucleus. Ndclea testd oblique ovatd suhti'igond, l/eviusculd nitidd. 

 ^' Shell obliquely heart-shaped and somewhat triangular, glossy 

 and nearly smooth. 



Tab. nost. 13, fig. 4. 

 Area Nucleus. Linn. Syst. Nat. p. 1143. 

 Gmelin, Syst. p. 3314. 

 Turton, Linn. Syst. iv. p. 267. 

 Pennant, Brit. Zool. iv. p. 217. 

 Donovan, Britisli Shells, ii. tab. 63. 

 Montagu, Test. Brit. p. 141. 

 Linn. Trans, viii. p. 95. 

 Turton, British Fauna, p. 161. 

 Dorset Catal p. 37, tab. 12, fig. 6. 



