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NUCULANIDAE 337
valves). Concentric ribs fairly even, well-developed, numerous. Periostracum
light- to dark-brown. Commonly found in mud just below low-tide
mark.
Figure 71. Nut and Yoldia Clams, a, Nuculana teimisiilcata Couthouy, % inch
(Atlantic); b, Yoldia liinatiila Say, 2 inches (Arctic waters, both coasts); c, Yoldia
montereyensis DzW, i inch (California).
Nuculana carpenteri Dall
North Carolina to West Indies.
Carpenter's Nut Clam
About Vi inch in length, compressed, thin, translucent yellow-brown,
with a long, slightly upturning rostrum. Anterior end round. Umbones very
small, close together. Almost smooth except for minute, concentric growth
lines and microscopic axial scratches which are absent in dead, white valves.
Commonly dredged offshore from 10 to 100 or more fathoms.
Nuculana fossa Baird Fossa Nut Clam
Alaska to Puget Sound, Washington.
% to I inch in length, elongate, moderately fat and smoothish except
for small, pronounced, concentric ribs at the anterior end and on the beaks.
Dorsal area of rostrum smoothish, depressed and bounded by 2 weak radial
ribs. Periostracum dark- to light-brown. Dredged offshore in shallow water.
Some workers consider the following forms or variations as subspecies:
sculpta Dall, vaginata Dall and curtulosa Dall.
Subgenus Ledella Verrill and Bush 1897
Nuculana ?nessanensis Seguenza Messanean Nut Clam
Cape Cod to the West Indies.