OF THE UNITED STATES. 307 



surf in considerable numbers, whilst in pursuit of 

 them. 



AMPHIDESMA, Lam. 



Species. 



1. A. *orbiculata. Shell orbicular, somewhat com- 

 pressed ; beak nearly central, aud a little prominent ; 

 posterior slope a little concave near the beak ; lunule 

 small ; valves slightly wrinkled transversely ; an- 

 terior submargin with an obsolete very obtuse undu- 

 lation, and with a few longitudinal obsolete lines ; 

 colour dirty white ; hinge with two lamellar teeth, 

 the posterior one placed near to the primary tooth, 

 and shorter than the anterior one ; interior ligament 

 cavity profound, fusiform, parallel with the anterior 

 slope, originating at the extreme tip of the beak, and 

 terminating nearly opposite to the middle of the an- 

 terior lamellar tooth. 



Length one inch and one-tenth. 



Breadth one inch and one-tenth. 



Inhabits the coast of Georgia. 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



Appears to be a rare species ; the largest I have 

 seen is one inch and two-fifths in breadth. 



2. A. *cequalis. Shell orbicular, slightly oblique, 

 polished, white, with very minute and numerous con- 

 centric wrinkles near the margin, which are obsolete 



