1. Genus Solen. Pl. [VI].

Animal. Body cylindroid, much elongated; the mantle in form of a canal open at both ends, closed in the rest of its extent by a thick epidermis which surrounds it; a cylindroid anterior foot.

Shell. Equivalve, extremely inequilateral, the summits very small, and entirely at the commencement of the dorsal line; one or two teeth in the hinge. Inhabits the seas of America and Europe. Twenty-one species.

2. Genus Panopæa. Pl. [VI].

Animal. Unknown.

The situation of the ligament, and the prominency of the apex, are the characters which distinguish it from the Mya.

Shell. Regular oval, elongated, gaping at both ends, equivalve, inequilateral; summit little marked and anterodorsal; hinge complete; similen formed by a conical primary tooth, before a short, compressed, ascending callosity, ligament exterior, attached to the callosity; two muscular impressions. Inhabits the Mediterranean Sea. One species.

3. Genus Solecurtus. Pl. [VI].