NUCULANIDAE 



337 



valves). Concentric ribs fairly even, well-developed, numerous. Periostra- 

 cum 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. 



