4 CAllDIADiE. 



as they came near our own epoch, when but two or three 

 allies of them are found. 



Cockles inhabit all depths of water, from the sea-shore 

 at tide-mark to the deepest sea-beds as yet explored ; but 

 each species has a very definite range, and the succession of 

 representative forms is as well marked bathymetrically as it 

 is in horizontal space and in time. Sand, or sandy-mud is 

 their usual habitat, and in it they lie buried, often in pro- 

 digious numbers. 



Dr. Carpenter has examined the microscopic structure of 

 the shell in this genus, and states that there is a tubular 

 texture in the external layer, but little organic structure 

 in the internal. 



C. AcuLEATUM, LinnsBus. 



Large, swollen, not solid ; ribs about twenty in number, rather 

 depressed, armed with compressed prickles ; their interstices 

 almost smooth. 



Plate XXXIII. Fig. 1. 



Cardium aculealum, Linn. Syst. Nat. ed. 12, p. 1122. — Penn. Brit. ZooI.ed. 4, 

 vol. iv. p. 90, pi. SO, f. 37.— Da Costa, Brit. Conch, p. 

 175. — DoNOV. Brit. Shells, vol. i. pi. 6 (not well). — 

 Mont. Test. Brit. p. 77, and Suppl. p. 30. — Linn. Trans, 

 vol. viii. p. 62. — Turt. Conch. Diction, p. 28. — Turt. 

 Dithyra Brit. p. 180, pi. 13,f. 6, 7.— Flem. Brit. Anim. 

 p. 420. — Brit. Marine Conch, p. 93. — BRO^^•N, lUus. 

 Conch. G. B. p. 87, pi. 34, f. 1, 2, 3.— Chemn. Conch. 

 Cab. vol. vi. p. IGl, (in part) pi. 15, f. 156.— Poli, Test. 

 Sicil. pi. 17, f. 1, 2, 3.— Wood, General Conch, p. 207, 

 (not variet}',) pi. 48. — Dillw. Recent Shells, vol. i. p. 

 114. — Lam. Anim. s. Vert. (ed. Desh.) vol. vi. p. 397. — 

 Philippi, Moll. Sicil, vol. i. p. 50, and vol. ii. p. 37. — 

 SowERBY, Conchol. Illustrations, Cardium, f. 28. — 

 Hanl. Recent Shells, vol. i. p. 131. — Reeve, Conch. 

 Iconica, Cardium, pi. 4, f. 17. 

 „ ciliare, (YOUNG.) Penn. Brit. Zool. ed. 4, vol. iv. p. 90, pi. 50, f. 



39. — Pulteney, in Hutchins, Dorset, p. 31. — Donov. Brit. 



Shells, vol. i. pi. 32, f. 2.— Mont. Test. Brit. p. 79.— Linn. 



