TRENTON CONGLOMERATE OF RYSEDORPH HILL . 103 



The observation of a succession of terranes from west to east 

 in Albany county, which proved to represent the Lorraine, Utica, 

 middle Trenton and Normans kill graptolite epochs, forms the 

 basis of the claim that the last must be homotaxial with part 

 of the lower Trenton limestone of the regions farther we«st. It 

 was further demonstrated by the observations of Prosser and 

 Cumings that the Trenton limestone thins out gradually from 

 the type section at Trenton Falls toward the Hudson river, while 

 at the other side of that river, according to the observations of 

 Walcott, Dwight and Dale, the Trenton epoch is only slightly 

 represented by calcareous deposits, and these most probably 

 belong only to the lowest Trenton. It is, hence, quite certain 

 that the Trenton in this part of the Appalachian region is largely 

 represented by clastic sediments. 



This distinct lithologic development is associated with an 

 entirely different faunistic facies, the Xormans kill graptolites 

 in association with a few small brachiopods constituting the only 

 evidences of life in these lower Trenton shales. It has been 

 pointed out that this peculiar graptolitic fauna has been traced 

 from Lower Canada, where it was studied by Lapworth, through 

 Maine, Vermont, and along the Hudson river in New York, and 

 probably, as maintained by Emmons, extends as far as Virginia. 

 While it has been identified by Lapworth with a fauna of wide 

 extent in the lower Siluric of Great Britain and Scandinavia, it 

 has not been recognized in its typical development west of the 

 Appalachian region, though apparently reappearing in Arkansas 

 and British Columbia. The consensus of opinion of recent writers 

 on this graptolite fauna is that it was of oceanic and probably 

 planktonic habitat. Its distribution on both sides of the Atlantic 

 basin indicates its extent over a large part of that basin. The 

 black bands filled with graptolites are in most of the localities, 

 hidden away in a huge mass of more sandy shales and thin beds 

 of sandstone, suggesting thus that the myriads of these living 

 beings were swept together only accidentally. The astonishing 

 scarcity of complete colonies among the endless numbers of 



