PLEIOCENE FOSSILS. 23 



This shell, in the fossil state, is larger than any specimens that we have seen of the recent 

 form of the species ; in every other respect it agrees perfectly with C. arctnella, of our 

 coast. 



Plate VII., Fig. 4. Side view of fossil, natural size. 

 " 5. View of interior of lower valve. 

 " 6. Upper view of lower valve. 



Locality. Royal Landing, Waccamaw. 



Museum, College of Charleston, 8. C. 



CHAMA CONGREGATA.— Con. 



Plate TIL, Figs. 7, 8, 9, 10. 



Ghama congregata, Con., Am. Jour. Sci., Vol. XXIII., p. 341, Foss. Ter. Form. p. 32, pi. XVII., fig. 2. 



C testa orbiculari, crassa, lamellosa • lamellis numerosis, brevissirnis • valva superiore 

 operculiformi ; valva inferior e convexa. 



Description. Shell orbicular, thick, lamellar ; plates numerous, very short ; upper valve 

 operculiform, covered with numerous short corrugated scales ; lower valve convex, scales 

 more distant, and often with radiating undulations. In some varieties of this fossil, the 

 beaks are produced, distant and much curved, resembling the genus Diceras. Both in 

 this and the preceding species, the lamella? often fall off, which greatly alters the aspect of 

 the specimen. 



C. congregata is often found in groups cemented together. 



The genus Chama makes its appearance in the middle Cretaceous, and is continued into 

 the actual period, where it abounds. 



Plate YIL, Fig. 7. Upper view of fossil, natural size. 



" 8. Side view of the same. 



" 9. Interior of lower valve. 



" 10. Interior of upyper valve. 



Locality. Waccamaw. ' 



Museum, College of Charleston, S. C. 



