Page:American Seashells (1954).djvu/535

Rh DON ACID AE 437 A bra aequalis Say Common Atlantic Abra Plate 30V North Carolina to Texas and the West Indies. 1/4 inch in size, orbicular, smooth, glossy and rather inflated. Surface may show a slight iridescence. Periostracum very thin and clear yellowish. Anterior margin of right valve grooved. A very abundant and very simple- looking bivalve. Compare with lioica. Abra lioica Dall Dall's Little Abra Plate 3ov Cape Cod to south Florida and the West Indies. M inch in size, similar to aequalis, but the beaks are nearer the anterior end, the shell is thinner, and more elongate. Anterior margin of right valve not grooved. The prodissoconch at the beaks is large, tan and more trigonal in shape than the adult. Common from 6 to 200 fathoms. Family DONACIDAE Genus Donax Linne 1758 The posterior end is the shortest and the fattest. 2 cardinal and an ante- rior and a posterior lateral in each valve. Pallial sinus deep. Donax variabilis Say Coquina Shell Plate 3or Virginia to south Florida and Texas. V2 to % inch in length. Ventral margin of the valves straight and almost parallel with the dorsal margin. The thinner, anterior end is commonly smooth, but may be microscopically scratched with radial Unes. From the middle of the valve to the blunt posterior end, small radial threads appear which become increasingly larger posteriorly. Internal margin of valves minutely denticulate. Color variable and commonly very bright, especially inside: white, yellow, pink, purple, bluish, mauve and commonly with rays of darker shades. The subspecies roemeri Philippi (pi. 3oq) is very common along the Texas shores. The posterior end is blunter, the whole shell not so elongate, and the ventral margin sags down. Donax fossor Say Fossor Donax Long Island, New York, to Cape iVIay, New Jersey. Never exceeds Vo inch in length, very similar to variabilis, but almost