108 History of the Geology of New York Island. 



This species is very closely allied to Gl. Jayana from Aus- 

 tralia ; the margins are, however, more rounded, the epidermis 

 is not of so brilliant a green, and the teeth are somewhat dif- 

 ferent. Compared with Gl. rugosa from Manilla, the margins 

 are more rounded, the valves are fuller, and the teeth are 

 larger. 



X. — Report upon the Past and Present History of the 

 Geology of New York Island. 



By It. P, Stevens. 

 Eead January 16, 1S65. 



The Past History of the Geology of Neiv York Island. 



In 1816, Mr. Hayden, in the Geological portion of Prof. 

 Cleveland's Mineralogy, describes a granite ridge, crossing 

 New York Island, and appearing at Hurlgate on Long Island, 

 thence extending into Connecticut. 



It is almost needless at this time to say, that there was no 

 such "granite ridge," there is only an elevation of gneiss 

 (Murray Hill), common to the whole island. 



In the same volume, Maclure, the father of American 

 Geology, upon his Geological Map of the United States, places 

 the rocks of the island with his primitive formation. 



In 1820, Samuel Akerly, one of the Yice-Presidents of this 

 Society, published " An Essay on the Geology of the Hudson 

 River, and the adjacent regions; illustrated by a geological 

 section of the country from the neighborhood of Sandy Hook 

 in N. J., northward through the Highlands in New York, 

 towards the Cattskill Mountains." The paper was read before 

 the Lyceum in August, 1819. 



At the time of its publication, it was a very valuable contri- 

 bution to the geological history of the Island, connecting it, as 



