10 POST-PLEIOCENE FOSSILS. 



rugose, or radiately undulating ; superior valve smaller, somewhat flat, lamellar or plicate ; 

 muscular impression nearly central; hinge with deep channel in lower valve, and cones- 

 ponding eminence in the upper, extending to apex of shell. 



It is exceedingly variable in form and character, both in a fossil and recent state. 



Notwithstanding its great abundance in the recent state along our shores, it is by no 

 means a very common shell in the Post-Pleiocene. In the Pleiocene it is a rare fossil. 



The long and narrow variety is known on the Carolina and Georgia coasts, as the Racoon 

 Oyster, and is described in the next article. 



Plate II. Fig. 9, Interior of lower valve, natural size. 



Locality. Charleston; Simmons', Young's Island; Brown's, St. Andrew's; Ashley 

 Ferry. Museum, College of Charleston, Cabinet F. S. H. 



OSTEEA V I E G I N I A N A . Variety, PEOCYON. 

 Plate II. Pig. 9a. 



Vulgo, Raccoon Oyster. 



Description. Shell narrow, greatly elongated, seldom curved, gradually widening from 

 the beak or apex to the other extremity which is rounded ; ligamental fossa long and deep ; 

 cavity often extending under the hinge in lower valve; its other characteristics are the 

 same as described above in O. Virginiana. 



In a recent state, it is a very common shell along the bays and shallow inlets of the 

 coast of South-Carolina; its elongated, narrow form, is due to its position, growing verti- 

 cally, and in crowded clusters. Individuals are frequently found measuring ten or twelve 

 inches in length, but seldom over one-and-a-half or two inches in breadth. Beds of this 

 species are often exposed at half-tides, at the mouths of rivers and creeks ; on the mud-flats 

 they abound. The Raccoon (Procyon lotor) resorts to these places upon the first flow of 

 the tide, when the mouths of the Oysters are all opened ready for the refreshing influence 

 of the young flood-tide ; quickly and skilfully, by a thrust of his paw, he extracts from 

 the shell his favorite food; hence the name, "Raccoon Oyster." 



In the Pleiocene marls of our State, we have found this variety fossil, but it is rare. 

 Only a few specimens have been discovered in the beds of Waccamaw and Goose Creek; 

 and though not abundant in the Post-Pleiocene, it is not uncommon. 



" The genus Ostrea had its beginning in the Triassic, was very numerous in the 

 Jurassic, Cretaceous and Tertiary periods, and has its numerical maximum in the present 



