340 American Seashells 



Genus Yoldia MoUer 1842 



Somewhat similar to Nuculana, but the valves are much thinner and 

 fragile, rarely with a long rostrum, usually gaping at both ends, much 

 smoother and glistening. 



Subgenus Yoldia s. str. 

 Yoldia limatula Say File Yoldia 



Figure 71b 



Maine to Cape May, New Jersey. Northern Alaska. 



I to 2 ^ inches in length, elongate, narrowing at the posterior end. Um- 

 bones very small, halfway between the ends of the shell. Exterior glistening 

 greenish tan to light chestnut-brown, with only faint concentric growth 

 lines. Interior glossy white. A rather common species just below low-water 

 mark. Distinguished from Y. sapotilla by its more elongate shape. It is pres- 

 ent in northern Alaska, but it is replaced to the south by the following sub- 

 species. 



Yoldia limatida gardneri Oldroyd Gardner's Yoldia 



Southern Alaska to off San Diego, California. 



Very similar to the true Innatida, but always having the anterior ventral 

 margin with a small concave depression. In general shape it falls within the 

 variations of the Atlantic specimens. Moderately common. 



Yoldia sapotilla Gould Short Yoldia 



Plate 27b 



Arctic Seas to North Carolina. 



% to 1% inches in length, oblong, smooth, with a moderately extended 

 posterior end. Periostracum yellowish to greenish brown. Differing from 

 limatula in being shorter and less extended and more truncate at the poste- 

 rior end. Commonly dredged off New England in shallow water; often 

 found in fish stomachs. This species can be confused with the uncommon 

 Y. myalis Couthouy (pi. 2 yd) which is found from Labrador to Cape Cod 

 and Alaska and which, however, is shorter and more pointed at the posterior 

 end. 



Subgenus Megayoldia Verrill and Bush 1897 

 Yoldia thraciaejormis Storer Broad Yoldia 



Plate 276 



Arctic Seas to Cape Hatteras, North Carolina. Alaska to Puget Sound. 



