which are almost obsolete on the disk and umbo : beaks 

 subcentral, a little prominent : postetior margin rather lon- 

 ger and much more obtusely rounded : hinge margin 

 nearly rectangular : umbonial slope with a slight undula- 

 tion : ftnterior margin subangulated at base : cardinal teeth 

 two in each valve, posterior one much thicker and more 

 prominent ; the anterior one of the right valve is obsolete : 

 remote from the cardinal teeth in the left valve, on each 

 side is a long and deep groove, which receives the corre- 

 sponding edge of the right valve : right valve destitute of 

 any appearance of lateral grooves or lateral teeth. 



OBSERVATIONS. 



This is allied to the A. tentie and Boysii^ Montagu, of 

 the coast of England, of which however I have not any 

 good description or specimen to compare, and it may pos- 

 sibly prove to be tlie same with one of these, when com- 

 parison shall be made. 



Since my quoted description was given, many speci- 

 mens have been found on the coast of Charleston, for which 

 I am indebted to the late Mr. Stephen Elliott. 



It belongs to the genus Abra of Leach. 



REFERENCE TO THE PLATE, 



The two lower exterior figures represent the natural size ; the upper cn^ 

 are somewhat enlarged, the right one exhibiting the interior view, and the left 

 on* is a detail of the cardinal characters. 



PLATE XXVUI. 



