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CARDITIDAE 379
each other, located nearer the anterior end. Lunule narrow, rough, ill-
defined. Numerous strong radial ribs are weakly beaded. Color whitish with
a rose tint. Moderately common from i foot to 70 fathoms on sandy bot-
toms. Compare with the commoner and closely resembling Venericardia
tridentata.
Genus Venericardia Lamarck 1801
Shell rounded-trigonal, with strong radial ribs which are commonly
beaded; internal margins crenulate; right anterior cardinal and laterals absent.
No byssus made.
Subgenus Cyclocardia Conrad 1867
Cyclocardia has whitish shells and a rough periostracum.
Venericardia borealis Conrad Northern Cardita
Labrador to Cape Hatteras.
Plate 28t
I to i^ inches in height, rounded, obliquely heart-shaped, thick and
strong; beaks elevated and turned forward. Surface with about 20 rounded,
moderately rough or beaded, radial ribs. Shell white, usually covered by a
fairly thick, velvety, rusty-brown periostracum. Lunule small but very deeply
sunk. Hinge strong; in the left valve the central tooth under the beak is
large, triangular and curved. Very common on the Grand Banks where it
serves as a food for fish.
V. novangliae Morse (Nova Scotia to New York) is similar, but is ovate,
the length being slightly greater than the height of the shell. It is sometimes
considered a variety of borealis.
Venericardia ventricosa Gould Stout Cardita
Puget Sound to Santa Barbara Islands.
Plate 29I
About % inch in length, rounded-trigonal, moderately fat, lunule small;
with about 1 3 rather wide, radial ribs which are bluntly beaded. Inner margins
of the valves have prominent, squarish, widely spaced crenulations which
correspond to the external ribs. There are two other forms, one from Mon-
terey (stearnsi Dall), the other from Redondo Beach, which are very close,
but their distinctiveness and proper names are yet to be decided. The latter
form is V. redondoensis "Burch" P. Morris 1952. C. ventricosa is dredged
fairly commonly.