CARDILIA. Desh. _Fam._ Cardiacea, Lam. A genus formed for the reception of Isocardia semi-sulcata, Lam. and a small fossil shell, which Deshayes had formerly named Hemi-cyclonosta Michelini; thus described, (translation) "shell oval, oblong, longitudinal, white, heart-shaped, ventricose, with large prominent umbones; hinge with a small cardinal tooth and a pit at the side; a spoon-shaped projection for the reception of the internal ligament; anterior muscular impression rounded, not deep; the posterior being upon a thin, horizontal lamina, projecting in the anterior." Deshayes further remarks that although the animal is unknown, the relations of the genus may be established by means of the shell alone. Two families contain all the shells which have the internal ligament inserted in a spoon-shaped projection; in the one, that of the Anatinæ, the ligament is supported upon a little bone, which is not soldered to the hinge; in the other, that of the Mactraceæ, this little bone has no existence. In the former, all the shells are inequivalve; in the latter equivalve. And M. Deshayes, considering that the valves are equal, and that there is no separate bone to the hinge, is of opinion that the genus ought to be placed near the Lutrariæ, and not far from the Anatinæ. C. semisulcata, fig. 501, 2. CARDINAL MARGIN. The edge of a bivalve shell on which the teeth is placed. CARDINAL TEETH. The teeth upon the hinge directly beneath the umbones of a bivalve shell, as distinguished from the lateral teeth, which are placed at a distance on each side. In Venus, fig. 119, the cardinal teeth, are marked by the letter c. CARDIOCARDITES. Bl. A genus separated from CARDITA, Auct. Thus described (translation) "oval species, with the inferior margin nearly straight, or a very little inflated, crenulated and completely closed. _Ex._ La C. Ajar, Adans Seneg. pl. 16. fig. 2." CARDISSA. _Sw._ A genus composed of those species of CARDIUM _Auct._ which are heart-shaped. _Ex._ C. dionæum, fig. 122. And C. Cardissa. CARDITA. Brug. _Fam._ Cardiacea, _Lam._ Submytilacea, Bl.--_Descr._ Equivalve, inequilateral, ovate, subquadrate or oblong, marked externally by ribs radiating from the umbones and terminating in a crenulated margin on the inner surface; cardinal teeth in one valve, one long, thick, oblique; another short, more straight; in the other valve one long, oblique, thick. Muscular impressions two in each valve, rather oval; palleal impression not sinuated.--_Obs._ This description includes Lamarck's genus Venericardia, which, although consisting of the more oblong species, is not considered sufficiently distinct to justify the separation. Cypricardia is distinguished from this genus by a remote lateral tooth. Mediterranean, Africa, East Indies, &c. Cardita calyculata, fig. 124.