74 PLEIOCENE FOSSILS. 



CRASSATELLA GIBBESII.— (New Species.) 

 Plate XX. Figs. 9 and 10. 



C. testa sub-trigona, crassa, concentrice sulcata; latere buccali rotundato; latere anali sub- 

 rostrato, angulato, longitudinaliter imicostato; umbonibus incurvis; lunula sub-excavata. 



Description. Shell somewhat triangular, thick, concentrically furrowed ; buccal side 

 rounded; anal side somewhat beaked, angular, with a longitudinal ridge; umbones 

 incurved ; lunule somewhat excavated. 



This well-defined species is easily distinguished from any of the varieties of the preced- 

 ing species. The umbones are much incurved and more inflated than in any form of C. 

 undulata. It differs from the Virginia and Maryland species in its more symetrical form 

 and greater regularity of the sulci, which mark the entire surface of the shell. The ridge 

 on the anal side is prominent, and produces an undulation which extends to the centre of 

 the shell. 



The species is very constant in its characters in every stage of growth. Fig. 10 repre- 

 sents a young shell. 



We have great pleasure in inscribing this species to our friend and co-laborer, Professor 

 L. R. Gibbes, of the College of Charleston. 



Plate XX. Fig. 9, Exterior of left valve. 

 " 10, Young shell. 



Locality. Waccamaw. 



Museum, College of Charleston. 



The living species of Crassatella are inhabitants of warm climates. The genus is 

 first found in the Cretaceous system, and has its greatest development in the Tertiary. 



