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346 American Seash ells
Subgenus Cunearca Dall 1898
Anadara brasiliana Lamarck Incongruous Ark
North Carolina to West Florida to Texas and the West Indies.
Plate 27y
I to 1V2 inches in length; almost as high as long. Beaks facing each
other at center of short, transversely striate ligamental area. Left valve over-
laps right valve considerably. Ribs 26 to 28, square with strong bar-like beads.
Periostracum thin, light-brown. A. mcongnia Say is this species.
A. chemnitzi Philippi from the Greater Antilles to Brazil is similar, but
thick-shelled, less than i inch in length; the beaks are slightly forward of the
center of the ligamental area.
Subfamily NOETllNAE
Genus Noetia Gray 1857
Beaks point posteriorly; valves the same size; ligament transversely stri-
ate; posterior muscle scar raised to form a weak flange.
Subgenus Eontia MacNeil 1938
The subgenus Eontia is an Atlantic group only. Noetia s. str. differs in
having decidedly more regular sculpture, the ribs smoother and never di-
vided; deeper and longer crenulations on the inner margin. There is only
one Recent American true Noetia (reversa H. and A. Adams) which occurs
from the Gulf of California to Peru.
Noetia ponderosa Say Ponderous Ark
Virginia to Key West, Louisiana and the Gulf of Mexico.
Plate 27Z; figure 28a
2 to 2 % inches in length, almost as high as long. Ribs raised, square and
split down the center by a fine incised line; 27 to 31 ribs per valve. Posterior
muscle scar raised to form a weak flange. Periostracum thick, black, but
wears off at the beaks. A common shallow-water sand-dweller. Fossil specimens
are rarely found on Nantucket, Massachusetts, beaches.
Family LIMOPSIDAE
Genus Limopsis Sasso 1827
Rather small, obliquely oval, clams with tufted, velvety brown peri-
ostracum. Hinge line curved, with a series of oblique teeth. The hinge
resembles that of the Glycymeridae. Ligament external, small, central, tri-