Sand Formation of the United States, 277 



eontain all the bivalves of which v^^e have spoken, and quantities of 

 belemnites. 



The calcareous beds of Gloucester county contain gryphsea, tere- 

 do, alcyonium? spatangus, and several species of Linnean madre- 

 pores. Crossing the Delaware river into the state of Delaware, we 

 find at St. Georges and its vicinity, great numbers of the genera 

 gryphsea, exogyra, and ostrea.* We have already adverted to the 

 multilocular shells of the deep cut of the Chesapeake and Delaware 

 canal, to which we may add the genus spatangus, and several other 

 genera of echinideae. The green sand below Annapolis, in Mary- 

 land, contains alcyonia. At Lynch's Creek, in South Carolina, exo- 

 gyrae occur, specifically the same with those of New Jersey and 

 Delaware. At Cockspur Island, in Georgia, the formation is recog- 

 nized by a prodigious quantity of belemnites. The localities here 

 enumerated will serve to convey a good idea of the productions of 

 nearly all the others. , 



Mineralogical Characters. 



These vary considerably ; but our marl most frequently presents 

 itself in minute grains, loose and friable, and of an uniform dull bluish, 

 or greenish color, often with a shade of gray. A hundred grains of 

 this variety gave Mr. Seybert the following constituents : 



Silex, ----- 49.83 



Aluraine, ----- 6.00 

 Magnesia, - - - - 1.83 



Potash, - - - - - 10.12 



Water, - - - - - 9.80 



Protoxide of Iron, - - - - 21.53 



Loss, ----- .89 



100.00 

 In a less cautious analysis by Mr. J. P. Wetherill and myself, of 

 an apparently similar marl from another locality, we obtained silex 

 49.00, protoxide of iron 30.00, alumine 5.50, lime 4.70, the re- 

 mainder being chiefly water and carbonic acid. Hence it appears 

 that the predominant constituents of these varieties of marl, are silex 

 and iron. They often contain beds of a dark bluish, tenacious clay ; 



* The same fossils appear to abound at Middletown Point, and its vicinity in N. J. 

 This locality, however, I have not been able to visit. 



