OF CONCHOLOGY. 63 



that the species was only a synonym of 0. fornicata, and owed 

 its supposed distinctive characters to its habitation ivithin uni- 

 valve mollusca. The specimens now shown are true unguifor- 

 mis, and are growing on the external surface of the Pecten. 



Mr. Tryon exhibited specimens of Mercenaria prceparca, Say, 

 and remarked that M. Mortoni, Conrad, and 31. fulgurans, 

 Tryon, had both proved to be synonyms of it, the latter being 

 the young shell. 



Mr. Wm. H. Dall was elected a Correspondent, and Mr. 

 Charles Wilson Peale a member of the Section. 



