308 MARINE SHELLS 



on the disk and umbo ; lateral teeth none ; primary 

 teeth two in the left valve and one in the other; in- 

 terior ligament cavity subfusiforni, as long as the ex- 

 terior ligament. 



Length two-fifths of an inch. 



Inhabits the southern coast. 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



A small species, not very commonly found. 



3. A. ^punctata. Shell orbicular, white, with 

 very minute, numerous, concentric wrinkles, and very 

 minute, numerous punctures; lateral teeth none; 

 primary teeth two in each valve, of which one has a 

 deep groove, which gives it a bifid appearance : 

 groove of the interior cartilage not very distinct: 

 within a small projecting rim or elevated line near 

 the edge, extends from the hinge to the basal margin. 



Length about seven-twentieths of an inch. 



Breadth much the same. 



Inhabits the southern shores. 



Cabinet of the Academy. 



This shell bears a strong resemblance to the pre- 

 ceding, on an exterior and transient view of its valves ; 

 but on examination it will be perceived to be more 

 orbicular and less oblique, and that the surface is less 

 polished. By the aid of a magnifier, the surface 

 will be observed to exhibit a remarkable punctured 

 appearance. 



