52 Bulletin 5 32-3 



146 FOSSIL SHELLS. 



teeth none : within obsoletely striated towards the 

 margin : posterior muscular impression perfectly 

 rectilinear, elongated, and oblique. 



Length one inch and nine-tenths, breadth two 

 inches and one- tenth. 



The posterior muscular impression is even more 

 elongated and slender than that of Y,. jamaicensis, 

 Chemn. In outline it is like L. scabra, Lam. The 

 impressions both before and behind the beaks are 

 very slender and contracted. A young specimen 

 belonging to the Academy, was brought from 

 Maryland by Mr. Jacob Gilliams. 



2. L. anodonta. PI. x. fig. 9. Orbicular, slightly 

 transverse, compressed ; teeth obsolete. 



Description. Shell with elevated wrinkles ; or- 

 bicular, a little transverse, with a very slight im- 

 pressed longitudinal line on the anterior margin : 

 anterior and posterior ends equally curved : apices 

 not prominent beyond the general curve of the 

 shell, with a very short deep emargination behind 

 them ; teeth obsolete ; both the cardinal and lateral 

 ones are generally altogether wanting : lunule 

 short, cordate, profound. 



Length from the apices to the base one inch 

 and one-tenth, breadth one inch and one-fifth. 



The impressed line on the anterior part of the 

 shell is hardly visible in many specimens, and is 

 sometimes only a very slight undulation, not ob- 

 servable but on close inspection. In the speci- 

 mens, the ligament of the hinge still remains, ap- 



[J. A. N. S., Phila., ist Ser., Vol. IV, 1824.] 



