1880.] NATURAL SCIENCES OF PHILADELPHIA. 31 



Feet in Thickness. 



the highl}^ fossiliferous stratum found at water mark, at Beckett's, 

 is probably represented by a bed of clay three feet in thickness, 

 commencing at a height of five feet, and which contains " great 

 numbers of black, water-worn, siliceous casts of small shells, 

 chiefly Turritella, the species not yet determined." Below this 

 an entirely new deposit now makes its appearance, a bed of clay 

 of five feet thickness, characterized by Ostrea percrassa and 

 Pecten Humphreysii. This last, therefore, probably represents 

 the most ancient post-Eocene deposit exhibited on the Chesapeake. 

 Ostrea percrassa and Pecten Humphreysii were also found by 

 Conrad at Huntingtown, Calvert County, where in a " depression 

 or small valley " a race-way had been excavated through the 

 fossiliferous ''marls." The lowest member of the section was 

 " quartzose sand, with casts of Perna maxillata.^^ On the east 

 bank of the Patuxent River, moreover, near the mouth of St. 

 Leonard's Creek, Conrad observed innumerable casts of Perna 

 maxillata imbedded in a stratum of fine siliceous sand, and rest- 

 ing on tlie fragmentary rock considered by him as the " founda- 

 tion of the peninsula " (B. N. I., p. 184). 



We should naturally look for some deposit contemporaneous 

 with that occurring on the west bank of the Patuxent, at some 

 point northeast of that locality where a section may present itself. 

 This we find at Easton, on the Choptank, where the mol- 

 luscous fossil fauna corresponds very closely with that observed 

 on the former river. The deposits of the older period, on the 

 other hand, reappear in Cumberland County, New Jersey, in the 

 " Miocene marl " of Shiloh, containing the following assemblage 

 of fossils (Cook, " Geology of New Jersey," 1868, p. 297) : 



