INTRODUCTION. 



In Maryland and Virginia numerous isolated beds of sands and clays are found overly- 

 ing the Eocene marl. Mr. Conrad, the distinguished American palaeontologist, determined 

 after a careful examination of three hundred and forty-four species, that fourteen per cent. 

 of the fossil shells therein were of living species, and therefore, according to Sir Charles 

 Ly ell's classification, these beds were referred to the Meiocene period of the Tertiary. 

 Upon investigating similar beds in South-Carolina, we ascertained the number of recent 

 species to be far greater than this ; that the fossils common in the former were rare or even 

 missing in the latter, and that the characteristic species of the two formations were distinct. 



In the final report on the Geology of South-Carolina, made in 1846, these beds were 

 referred to the Pleiocene period, a newer division of the Tertiary; since then eleven years 

 have elapsed, during which time we have collected a number of fossils, and investigated 

 to a great extent, the lithological as well as palseontological characters of this interesting 

 formation, and now feel quite assured of the propriety of thus distinguishing them. 



Two hundred and three species are figured and described in the present work, eighty- 

 five, or about forty-two per cent, are known to be recent, and now living in the waters of 

 the present period, and when the existing fauna of our sea-coast shall be carefully studied, 

 the percentage will be greatly increased. 



Of the forty-six species restricted to the Pleiocene of this State, many also are without 

 doubt, still living upon the coast. 



From careful investigations the following tabular synopsis is presented of the extinct 

 and recent species found in the beds of New Jersey, Virginia, North and South Carolina: 



New Jersey, of 170 species, 22 are recent, = 13 per cent. 

 Virginia, " 160 " 29 " = 18 



North-Carolina, "80 " 27 " =34 



South-Carolina, "203 " 85 " =42 



c 



