Page:Natural History, Mollusca.djvu/303

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horizontal spoon-shaped process, belonging to the left valve, and corresponding to a horizontal groove or socket in the right. The ligament is internal, inserted between the socket and the spoon-shaped process. The shell is generally white, exhibiting rude concentric lines of growth, and covered with a wrinkled epidermis, which is continued over the mantle and tubes of the animal.

The mollusk, thus encased in a thick and leathery case, presents a close resemblance to one of those Tunicated Ascidiæ, which I shall presently notice, with the addition of a bivalve shell; "and no better mode could be devised of impressing on the tyro in malacology the close affinity of two great sections, so unlike in most of their proper members, than the placing before him, side by side, examples of the genera Mya and Cynthia.

The species of this genus are eaten not only by man; Otho Fabricius informs us, that on the inhospitable shores of Greenland, where they are numerous, they are greedily devoured by the walrus, the arctic fox, and by many predaceous birds, as well as by large fishes.

We have two native species, both of considerable size, of which the larger is the Sand Gaper (Mya arenaria), which attains a breadth of four inches, and a length of nearly two and a half. It is a coarse shell, of an earthy reddish or yellowish hue, stained with dirty black, and marked by irregular lines of growth. The animal, when its epidermis is stripped off, is yellowish-white, the orifices tinged with red; the investing coat is brown, rough, and wrinkled.

This Gaper is common on many parts of our seashore, in gravelly, clayey, or sandy ground, at low