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338 American Seashelh
% to % inch in length, moderately elongate, with a very short, slightly
pinched rostrum. Almost smooth except for a few very small concentric
growth ridges near the base of the shell. When alive, glistening light-brown
with a slight oily iridescence. When dead, grayish white with concentric
chalk streaks. Commonly dredged in moderately deep water. One of our
smallest species.
Subgenus Saccella Woodring 1925
Nuculana acuta Conrad Pointed Nut Clam
Cape Cod to the West Indies.
% to % inch in length, moderately elongate, with a sharp-pointed poste-
rior rostrum. Concentric ribs evenly sized and evenly spaced and extending
over the rib which borders the dorsal surface of the rostrum. Shell usually
dredged dead in a white condition. Periostracum thin, very light yellowish.
Common offshore.
Nuculana concentrica Say
Northwest Florida to Texas.
Concentric Nut Clam
^ to % inch in length, strong, rather obese and moderately rostrate.
Yellow-white, semi-glossy and with very fine, concentric grooves which are
evident in adults on the ventral half of the valves. Beaks and the area just
below smooth. Radial ridge on rostrum smoothish, not crossed by strong
threads. Differing from acuta in being more obese, in having a smooth beak
area, smooth rostral ridge and in having much finer, more numerous, con-
centric threads or cut lines. Moderately common in i to 3 fathoms.
Figure 72. Pacific Coast Nut Clams, a and b, Nuculana taphria Dall, % inch
(California); c, Acila castrensis Hinds, ^> inch (Pacific Coast).
Nuculana taphria Dall
Bodego Bay, California, to Lower California.
Taphria Nut Clam
Figure 72 a, b