Page:American Seashells (1954).djvu/441

Rh Family PTERIIDAE Genus Pteria Scopoli 1777 Fairly thin-shelled, moderately fat, and with the hinge ends considerably drawn out. Pearly inside. The right and left valves bear i or 2 small denticles which fit into shallow sockets in the opposite valve. Pteria colymbiis Roding Atlantic Wing Oyster Plate 35d North Carolina to southeast Florida and the West Indies. I /4 to 3 inches in length, obliquely oval with a long extension of the hinge line toward the posterior end. Left valve inflated. Right valve somewhat flatter and with a strong anterior notch for the byssus. Periostra- cum matted, brown and with cancellate fimbrications. Exterior color vari- able: brown, black or brownish purple with broken, radial lines of cream or white. Interior pearly with a wide, non-pearly margin of purplish black with irregular cream rays. Common from low water to several fathoms. The Western Wing Oyster, Pteria sterna Gould is very similar, 3 to 4 inches in length, and deep purplish brown with occasional paler rays. An- chored in mud; from San Diego to Panama. Common. Genus Pinctada Roding 1798 This is the famous genus of pearl oysters. The byssal gape is in the right valve below the small, triangular auricle. Margaritifera Schumacher is a synonym. Pinctada radiata Leach Atlantic Pearl Oyster Plate 35c South half of Florida and the West Indies. 1% to 3 inches in length, moderately inflated to flattish, thin-shelled and brittle. There is a small, thin, flat ligament at the center of the hinge. Exterior tan with mottlings or rays of purplish brown or black. Rarely tinted with dull-rose or greenish. In quiet waters, thin scaly and very deli- cate, periostracal spines may be developed. Interior a beautiful mother-of- pearl. Common in shallow water attached to rocks. Family PINNIDAE Genus Pinna Linne 1758 The Pen Shells are large, fragile, fan-shaped clams which live in sandy or mud-sand areas, usually in colonies. The apex or pointed end is deeply