CARDIUM. CONCHIFERA. 95 



dentated or plicated on their internal margin ; hinge with 

 four teeth in each valve, of which the two primary ones are 

 approximated and oblique, and two lateral distant ones. 



The shells of the greater part of this genus are furnished with longitudinal ribs 

 more or less prominent, often striated, or with imbricated scales or spines, but the 

 interior of the valves is never furrowed but towards the margin. In all the species 

 the ligament is exterior, very short, and the muscular impressions, two in number, 

 very indistinct. The animal is provided on one side with two unequal tubes, 

 ciliated at their orifice, and on the other with a large muscular foot. Cockles are 

 generally found buried in the sand near the shores, and are found in every sea. The 

 fossil species are numerous ; and it is worthy of remark that some of those found in 

 Europe in this state have their living prototypes in the seas of Asia. In Britain 

 they are found in carboniferous limestone, lias, oolite, green-sand, and London clay. 

 Fleming, 423. 



C. coslatum, Lin. Shell gibbous, equivalve, with projecting cari- 

 nated, concave, membranaceous, longitudinal ribs ; anterior side 

 gaping ; colour pale tawny, and the ribs white. 3 or 4 inches 

 long. Inhabits African seas Lister, pi. 327, % 164. 



C. ringens, Lam. Shell rounded, longitudinally ribbed, with the 

 anterior margin deeply serrated and gaping ; colour white, tinged 

 with rose-colour on the margin. 1 inch long. Inhabits Ameri- 

 can seas Lister, pL 330, fig. 167- 



C. echiiiatum, Lin. The Spined Cockle. Shell somewhat heart- 

 shaped, with rather remote longitudinal ribs, armed along the 

 middle with a spinous elevated line, and striated transversely. 2 

 inches long. Northern seas. B, Browns Illust. pi. 21, fig. 6, 7, 8. 



Dr Fleming is of opinion that the C. aculeatum and C. tiibcrculatum, Lin., with 

 the present, are merely varieties of one species, varying in the number of their ribs 

 from 16 to 21, from smooth to coarsely wrinkled, and from sharp, pointed, and re- 

 curved spines to broad and blunt tubercles ; and that the C. ciliare of Linneeus is 

 the young. 



C. isocardia, Lin. Shell oblique, heart-shaped, tumid, with thirty- 

 five longitudinal ribs, and erect vaulted scales ; outer surface 

 whitish, with irregular reddish brown spots ; inside white, stained 

 with purple. 2 inches long. Inhabits American seas. D'Ar- 

 genv. pi. 23, fig. M. 



C. edule, Lin. The Common Cockle. Shell antiquated, with twen- 

 ty-six longitudinal ribs, and transverse wrinkled somewhat imbri- 

 cated striae ; colour whitish or pale ferruginous. 1 J inch long. 

 Inhabits European coasts. B Wood's Conch, pi. 55, fig. 4. 



This is the most common British species, and found on all the sandy shores. It is 

 frequently collected for sale. 



C. icevigatum, Lin. The Smooth Cockle. Shell subovate, obsolete- 

 ly ribbed longitudinally, except at the two ends, which are near- 

 ly smooth, and covered with a brownish olive glossy epidermis. 

 2 inches long. European seas. B. Penn. Brit. Zool. iv. pi. 54. 



C. unedo, Lin. Shell subcordate, turgid, white, spotted with pur- 

 ple ; ribs armed with scattered;, elevated, crescent-shaped, co- 

 loured striae. If inch long. Inhabits Indian seas. Humph. 

 Mus. pi. 44, fig. F. 



