Handbook of Paleontology 169 



sandy beach. The shell has a length of one and a quar- 

 ter inches to two and one-half inches and a width of one- 

 half to three-quarters of an inch. It is dull white, orna- 

 mented with transverse ribs, of a thin chalky texture and 

 gaps widely at the posterior end. A Petricola (P. car- 

 ditoides) of the Calif ornian coast has similar habits, but 

 bores into soft rocks instead of clay. The little Nut Shell 

 (Nucula proximo) is the common Nut Shell of the At- 

 lantic coast to North Carolina, and also occurs in western 

 Florida. It is the commonest of several species found 

 along the New England coast where it exists in countless 

 thousands in all the bays and harbors, in muddy or pebbly 

 situations near the shore. The shell is a quarter of an 

 inch long, has a light olive epidermis and nacreous inte- 

 rior. Another species-, the Thin Nut Shell (N. tenuis) 

 is found northward from Maine and along all the coast 

 of northern Europe. It is about as big as a grain of 

 corn, the shells are thin with a bright green epidermis. 

 There are a few other species found on our colder coasts, 

 and also in deep water from California to Alaska. A 

 larger shell than the Nut Shell is the Finely-grooved Leda 

 (L. tenuisulcata). The shell is about an inch long and 

 narrows to a blunt gaping point. There is a light green- 

 ish epidermis and the interior of the shell has a pearly 

 luster. This species is found in muddy bottoms in shoal 

 water on the New England coast and northward. With 

 this species, in the same situations, along the New Eng- 

 land coast is found the File Yoldia (Y. Umatilla) which 

 ranges southward to Cape Hatteras and is found on the 

 Pacific coast and the coast of Norway. The shell is one 

 to three inches long and the valves narrow posteriorly. 

 There is a glazed green epidermis and the interior of the 

 shell is light bluish and pearly. The Broad Yoldia 



