Cardium costatum. C. Indicum. C. ringens. C. Asiaticum. C. tennicostatum. C. fimbriatum. C. pseudolima. C. aculeatum. C. erinaceum. C. tuberculatum. C. Brasilianum. C. apertum. C. papyraceum. C. bullatum. C. ciliare. C. echinatum. C. lævigatum. C. biradiatum. C. eolicum. C. pectinatum. C. isocardia. C. muricatum. C. angulatum. C. marmoreum. C. elongatum. C. ventricosum. C. rugosum. C. sulcatum. C. serratum. C. unedo. C. medium. C. fragum. C. retusum. C. tumoriferum. C. rusticum. C. edule. C. Groenlandicum. C. latum. C. crenulatum. C. exiguum. C. minutum. C. roseum. C. scobinatum. C. hemicardium. C. cardissa. C. inversum. C. Junoniæ. C. lineatum.
_C. edule._ The edible Cardium, or common Cockle. Pl. 10, fig. 2.
Species not gaping, with about twenty-six depressed ribs and transverse obsolete scales; of a cream colour; beaks protuberant.
Species heart-shaped, valves angularly flattened, umbones alternating.
Species smooth or nearly so, anterior side as large as the posterior.
_C. hemicardium._ The half-heart Cardium.
Species ribbed, with elevated rough striæ; the anterior side is very short and almost flat.
No angle at the umbones; anterior side at least as large as the posterior; rows of white, hollow, elevated ribs, situated at regular distances, proceeding from the umbones to the margin, with the spaces between them of a reddish brown colour.
Species with ribs armed with small crescent-shaped scales.
_C. tuberculatum._ The tuberculated Cardium.
Species not gaping, with large ribs armed with nodules.
Lamarck took this genus from the Chama on account of several peculiarities in the shell as well as in the animal. It is not affixed to other bodies by its lower valve, but, according to De Blainville, lies exposed on the rocks. There is some difficulty in distinguishing this genus from the Venericardia, without carefully examining the position of the two teeth.
Shell regular, thick, solid, equivalve, more or less inequilateral; summit dorsal, always very recurved anteriorly; hinge similar, formed by two oblique teeth; one short cardinal placed beneath the umbo, the other oblique, arched, marginal, and prolonged; ligament elongated, sub-exterior, and inserted; two very distinct muscular impressions.