Shell. Of a somewhat variable form, generally striated longitudinally and much compressed, equivalved, more or less inequilateral; the anterior side almost always longer and more rounded than the posterior, which constantly presents a flexuous fold, at least at its inferior edge; summits feebly marked; hinge similar; one or two cardinal teeth; two lateral teeth, far apart with a pit at their base in each valve; ligament posterior, large; round muscular impressions. The finest species of this beautiful shell are found in the pearl fisheries of Ceylon; and numerous species on the American shore. Sixty-eight species.

5. Genus Tellinides. Pl. [VII].

Animal. As above.

This genus is very nearly allied to the Psammobia, Tellina, and Lucina, but upon close examination it will be found to be distinct from either.

Shell. Equilateral, transverse, somewhat elongated, nearly without the flexuous plait; two divergent cardinal teeth, of which the anterior is but little distant from the summit. Inhabits the Bay of Naples. Two species. One species is found on the shores of America.

6. Genus Corbis. Pl. [VII].

Animal. Differing slightly from the Lucina.

This genus was classed by Lamarck with the Lucina, but the great difference in the organization of the animals discovered by Cuvier, has made this a distinct genus.