COCHLODESMA. 235 



COCHLODESMA, Couthouy. 



Shell transversely ovate, rather compressed, thin, inequi- 

 valve, nearly equilateral. Surface nearly smooth, or mi- 

 nutely scabrous, with a fine epidermis. Muscular impres- 

 sions slight, connected by deeply sinuated palleal impres- 

 sions ; hinge formed of a spoon-shaped horizontal process in 

 each valve, connected by a cartilage. Ligament external 

 and slight ; internal surface of valves strengthened by ob- 

 lique divergent ribs. Beaks fissured. 



Animal, according to Couthouy, " compressed, mantle 

 closed, except anteriorly for the broad compressed foot ; 

 siphons long, slender, divided in their whole extent." Ac- 

 cording to Mr. Clark, the characters of the animal closely 

 resemble those of Thracia. 



This genus was founded by the distinguished American 

 conchologist, whom we have just quoted, for a small but 

 very distinct group of bivalves, previously confounded with 

 Thracia and Anatina, but conspicuously distinguished by 

 the peculiar structure of the hinge. 



C. PR^TENUE, Pulteney. 



Plate XV. fig. 4, 



Mya prcetcmds, Pulteney, in Hutchin's Dorset, p. 28. — Dorset Catal. p. 28, 



pi. 4, f. 7.— Mont. Test. Brit. p. 41, pi. 1, f, 2.— Linn. 



Trans, vol. viii. p. 37. — Donov. Brit. Shells, vol. v. pi. 176. 



— TuRT. Conch. Diction, p. 101. — Wood, General Conch. 



p. 94, pi. 24, f. 7, 8, 9.— DiLLW. Recent Shells, vol. i. p. 43. 



—Index Testae, pi. 2, Mya, f. 5. 

 Anatina prcBtenuis, Turt. Dithyra Brit. p. 48, pi. 4, f. 4. — Macg. Moll. Aberd. 

 p. 294— Brit. Marine Conch, p. 43.— Hanl, Recent 

 Shells, p. 23. 

 Amphidcsma pvcetcnue, Flem. Brit. Auim. p. 432. 



