A GEOLOGICAL HISTORY. 51 



been quarried in many places. At Hallet's Cove, 

 near the ferry, where it is beautifully striped, blue- 

 black and white, (giving it aribbon-like appearance,) 

 it is a good building stone. At Ravenswood, which 

 is a mile south, this rock does not quarry so well, 

 having none of its seams so easily opened — at 

 both localities its strata is vertical. This rock 

 may be traced to the salt-marsh, one mile north of 

 Wiiliamsburgh. 



3d Serpentine. — {Plate 3, fig. 3.) 

 4th Sandstone. — (Plate 3, fig. 4.) 

 5th Greenstone Slate, — (Plate 3, fig. 5.) 

 6th Trap. — (Plate 3, fig. 6.) The rocks of these 

 four formations have been described already under 

 their respective names. 



7th Green Sand. — (Plate 3, fig. 7.) New Jersey 

 Marl. It is more than probable that this member 

 of the Cretaceous Group underlies Long Island 

 and may be a continuation of the great range 

 which begins at the south, in Virginia, and runs 

 through New Jersey to the Neversink Hills, at 

 which place it is last seen above the surface. 

 Dr. J. C. Jay exhibited at the Lyceum of Natural 

 History on Monday, December 19th, 1842, a large 

 and beautiful specimen of the Exogyra Costata of 

 Say, of the same age and formation as those of 

 New Jersey. This specimen was given to him to 



