﻿UNITED STATES. 233 



have become so at maturity ; an old one is more emarginate than the one figured. 

 The old specimens are very dark on the umbones and light yellow at the inferior 

 margin. None had the beaks sufficiently perfect to give the character of the undu- 

 lations of the tips. On the posterior slope it is dark and roughly striate. It is with 

 much pleasure I dedicate this species to Garret Hallenbeck, Esq., to whom I am 

 indebted for so many fine Georgian Mollusca. 



