GEOLOGICAL SOCIETY OF PENNSYLVANIA. 



don clay and calcaire grossier, an opinion which e very- 

 subsequent discovery has tended to confirm, until it is 

 now beyond dispute and admitted by every American 

 geologist. To personal observation I am chiefly indebted 

 for the knowledge and relations of every locality of the 

 eocene hitherto described, occurring in New Jersey, 

 Virginia, Maryland, South Carolina, Georgia and Ala- 

 bama. Piscataway is situated in a beautiful valley, 

 bounded towards the Potomac by a range of diluvial 

 hills which repose on the horizontal strata of the eocene. 

 From the village the creek cuts through the same for- 

 mation to its junction with the Potomac at Fort Wash- 

 ington. It has been stated by Professor Ducatel, that 

 green sand of the age of the New Jersey marl" exists 

 in Maryland, but I believe that so far as organic remains 

 will determine the point, it will all prove to be of lower 

 tertiary origin. 



The only places where I have seen the eocene and 

 older pliocene in contact, are in the bank of James river 

 in Virginia, about two miles below City Point; and again 

 a few miles further down the river at Coggin Point, the 

 plantation of my friend Edmund Ruffin, Esq. These 

 localities have been noticed by Professor W. B. Rogers 

 and Mr Featherstonhaugh. The bank of the river is 

 high and precipitous ; the lower portion, having but a few 

 feet elevation, consists of eocene chloritic sand containing 

 abundance of Ostrea sellxformis, nobis. A thin seam of 

 gypseous clay is generally interposed between the green 

 sand and ferruginous marls, and characterized by the 

 above mentioned Ostrea^ which is thus brought in actual 

 contact with the pliocene fossils, but is never intermixed 

 with them. It was here I learned the curious fact that 

 the Ostrea compressirostra, Say, was the only species of 

 testacea destined to survive, in the same region, the re- 

 volution which destroyed all its associates of the eocene 

 ocean. It is abundant on both the tertiary divisions. 

 1.-2 s 



