CARDIUM. 231 



RIBBED COCKLE. 

 PL 58./. 1. Dr. Coombe. 



33. Cardiura costatum. C. testa gibba, eequivalvi, costis elevatis, cari- 

 natis, concavis, membranaceis. Linn. Syst. Nat. ed. 12. p. 1121. 



Shell gibbous, of equal valves, with high, keeled, concave, membrana- 

 ceous ribs. 



List. Conch, pi. 327. f. 164. Rumph. Mus. pi. 48, f. 6. Gualt. Test. 

 pi. 72. f. D. D'Argenville Conch, pi. 26. f. A. Favanne Conch, pi. 

 52. f. B. Adans. Conch, pi. 18. f. 2. Knorr Vergn. 1. pi. 28. f. 2. 

 Chem. Conch. 6. pi. 15. f. 151, 152. Encyclop. Method, pi. 293. f. 1. 

 a— c. 



A large, suborbicular shell, of a milk-white colour, 

 except between the middle ribs, where it passes from 

 light tawny to chocolate brown; it is extremely thin, 

 brittle, and transparent, when young, but becomes thick, 

 strong, and opaque in old age ; there are eighteen very 

 large channels, proceeding from the apex to the circum- 

 ference of the shell, forming so many high, sharp-edged, 

 ribs. The inside is grooved to correspond with the 

 ridges on the surface ; the teeth are large and strong ; 

 the middle is long and pointed. The largest specimens 

 measure four inches in length, and four inches and a 

 half in breadth. 



Inhabits the coast of Guinea, and the sandy shores of 

 Senegal, but is very rarely to be obtained perfect. M. 

 Adanson, who has particularly described this shell, 

 says that single valves only are thrown on the shore; 

 the animal, living in very deep water, cannot be dredged 

 up alive, and therefore very few cabinets possess this 

 shell entire, or with similar valves. 



