The Rock-eaters

Genus LITHODOMUS, Cuv.

Shell thin, cylindrical, inflated in front, wedge-shaped behind; surface finely striated, often wrinkled and furrowed; dorsal line short; beaks minute, incurved; epidermis thick, dark; lining pearly. When young, these mussels are suspended to rocks by the byssus. At maturity they bore into limestone rock and cannot turn around. The calcareous shell of Spondylus is often burrowed, especially of the ponderous species. The shell is often thickened by a limy deposit. The animal is luminous.

A small genus of forty species, well represented in the West Indies.

The Rock-eater (L. lithophagus, Linn.) is shaped like a pea pod, and has a smooth, chestnut exterior. It is found in coral rocks. Length, 2 to 3 inches.

Habitat.-Europe, West Indies, Florida Keys.

Genus LITHOPHAGUS, Muhlf.

The Plumed Rock-eater (L. plumula) Hanley, is very like the last. It burrows in rocks and old shells. Length, 1 to 2 inches.

The Mediterranean L. dactylus is highly esteemed as food.

Genus ADULA, H. & A. Ads.

The Pea Pod Shell (A. falcata, Gld.) is described by its name. The shell is thin and of the texture of rubber, white and pearly within, with a wrinkled brown epidermis. It is able to bore into very hard rock, forming a burrow to the sides of which it fastens itself by the byssus. Length, 2 to 3 inches.

Habitat.-California coast.