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 



