122 NEW YORK STATE MUSEUM 



communication between the open Atlantic and the interior Paleozoic 

 sea which existed during Ordovicic time. This bay was thus sur- 

 rounded by old-lands on the north, east and southeast, and its 

 waters appear to have been very shallow. We do not know just 

 what the conditions were under which the early Siluric deposits of 

 this region were made; for the lower beds are so barren of organic 

 remains, that we are forced to look for evidences other than that 

 furnished by fossils, of the physical conditions during this period. 

 It is not improbable that the waters of the early Medina sea were 

 cut off from the ocean at large, at least sufficiently to prevent a free 

 communication. This may not have been the case at first; for A r - 

 throphycus h a r 1 a n i flourished in these waters during the 

 deposition of the Oswego beds, 1 and this species characterizes the 

 rocks of late Medina age, during the deposition of which we have 

 reason to suppose that a junction of the Medina sea with the ocean 

 at large had been effected. 



Along the eastern and southeastern margin of this interior water 

 body were deposited the thick beds of conglomerate, which now 

 constitute the capping rock of the Shawangunk and other ranges 

 of hills, while farther west, at a distance from the source of supply, 

 the Oswego sandstone was accumulating. Later the character of 

 the deposit changed in this region, from the gray silicious sands to 

 the impalpable muds and fine sands of the lower Medina. What- 

 ever the source of these sands, ferruginous matter was plentiful, as 

 shown by the red color of the deposits, and this leads to the sup- 

 position that they were derived from' the crystalline rocks of the 

 Adirondacks and the Canadian highlands and not from Ordovicic or 

 Cambric deposits. 



It is not improbable that, during the early Medina epoch, the 

 waters of this basin were of a highly saline character. No deposits 

 of salt were formed, or if these existed, they were subsequently 

 leached out. The Medina beds are however rich in saline waters, 

 salt springs being common throughout this region, 2 and this may 



1 This species is found in the eastern part of the district, at the base of 

 the Oneida conglomerate. 



2 In the early part of the century salt was not infrequently manufactured 

 from these springs. 



