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FINNIDAE 359
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
North Carolina to southeast Florida and the West Indies.
Plate 35d
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. Periostracum
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. Anchored
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
South half of Florida and the West Indies.
Plate 35c
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