The Ark Shells Chest Shells - Family Arcidie

Mediterranean Sea, North Carolina to West Indies. 385 The Ark Shells. Chest Shells A. Americana, Gray, has a larger, more oblong shell, with more ribs, flat and each impressed with a median line. These characters distinguish the two species, which occur together from North Carolina to the West Indies.

A.

incongrua, Say, as broad as long, with wide ridges on the thin, unequal valves, is about two inches long and broad. The right valve is smaller, its ridges crinkled, especially behind the blunt umbones. North Carolina to West Indies.

A.

transversa, Say, is rhomboidal in outline broadening at the posterior end. Its ribs are deeply cut, marked by fine scaly striae, and crossed by a few deep, concentric lines. Epi dermis brown. Length, 1/ to 2 inches.

Habitat.

New England to Florida Keys.

The Ark (A. reticulata, Gmel.) a very small spe cies with cancellated surface, is found on the beaches of southern California. Specimens of other Mexican species sometimes stray northward into these waters. Such visitants are rare. A. reticu lata is found, also, from Cape Hatteras to the West Indies.

Genus PECTUNCULUS, Lam.

Shells orbicular in outline, with hinge teeth in a semicircle; ribs radiate, margins scalloped inside ; animal with large, cres cent-shaped foot, wavy-margined; mantle open, margins plain, with small ocelli ; lips continuous with gills. About sixty

living, eighty fossil species.

The Feathered Pectunculus (P_ pennaceus, Lam.) white, mottled with brown, has its beaks meeting at one end of the liga ment. It has the characteristic semi-circle of fine teeth lock ing the hinge. As in all ark shells, the number of teeth increases with the growth of the shell. Diameter, 2 inches, Habitat.— North Carolina to West Indies.

The Giant Pectunculus (P. giganteus, Rve.) was used by western Indian tribes of tropical America for personal adorn ment. Their graves contain armlets, a favourite ornament, made by grinding away all but the rim of the shell. The beaks were cut into pendents, rings and beads perforated for necklaces. Bits were inlaid in mosaic work. In Arizona graves of prehistoric tribes are found clay images of the Pectunculus. The sea shells are evi dently known, but rare, in a region far from their native sea.

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