254 LONG ISLAND. [CHAP. XVIII, 



the wind to the height of 40 or 50 feet, and inclose evergreen 

 oaks ( Quercus virens), the upper branches of which alone pro 

 trude above the surface. Between the parallel sand dunes were 

 salt marshes, where we collected the plant-eating shell called 

 Auricula bidentata, of a genus peculiar to such littoral situa 

 tions. On the sea-beach, we gathered no less than twenty -nine 

 species of marine shells, and they were of peculiar interest to me, 

 because they agreed specifically with those which I had obtained 

 from the strata lying immediately below the megatherium and 

 other fossils in Skiddaway Island, and which occur below similar 

 remains presently to be mentioned near Hopeton. In some places 

 we found bivalves only of the genera Pholas, Lutraria, Sole- 

 curtus, Petricola, Tellina, Donax, Venus, Cardium, Area, 

 Pinna, and Mytilus, just as in the fossil group. On other parts 

 of the beach there was a mixture of univalves, Oliva, Pyrula 

 (Fulgur), JBuccinum, &c. Besides these shells we found, scat 

 tered over the sands, a scutella and cases of the king crab (Li- 

 mulus&quot;), and fragments of turtles, with bones of porpoises. 



Every geologist who has examined strata consisting of alter 

 nations of sandstone and shale, must occasionally have observed 

 angular or rounded pieces of the shale imbedded in the sand 

 stones, a phenomenon which seems at first sight very singular, 

 because we might almost say that the formation is in part made 

 up of its own ruins, and not derived wholly from pre-existing 

 rocks. On the exposed coast of this &quot; frontier island,&quot; I saw a 

 complete explanation of the manner in which this structure orig 

 inates. Deposits of sand and beds of clay are formed alternately 

 at different seasons, arid at the time of our visit the sea was 

 making great inroads on an argillaceous mass, washing out 

 pieces of the half-consolidated clay, and strewing them over the 

 sands, some flat, others angular, or rolled into various sized peb 

 bles. These, when carried out into the adjoining parts of the 

 sea, must be often included in the sand, which may be eventually 

 converted into sandstone. 



Among the numerous sea birds, I particularly admired one called 

 the sheer-water, with its shrill clear note, and most rapid flight. 



On my return to Cannon s Point, I found, in the well-stored 



