452 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Five of the fossils thus common to Lower and Upper Silurian 

 strata are vouched for by James Hall, six by Daniel Sharpe, one by 

 De Verneuil, two by Conrad, and one by Emmons. I am incapable 

 of believing, as yet, that these pains-taking and experienced palaeon- 

 tologists have erred in their identifications ; and I feel fully entitled 

 to reason upon them as faithful interpretations of nature. 



I shall conclude these observations by stating that if we look at 

 the whole palaeozoic scheme, and the presence of recurrent fossils at 

 all periods of this vast epoch and in every known part of the globe, 

 we shall perhaps be of opinion that a way of escape from the Lower 

 to the Middle and Upper Silurian Stage in New York would be pro- 

 vided. And so it seems to be. In four localities these stages are 

 either in contact or approach each other closely, so as to admit of 

 the possible transmission upwards of the species of the Lower Stage 

 — not that molluscs have been seen in actual transition, where the 

 strata are close together. Doubtless in these shattered forest- and 

 swamp-covered wildernesses many similar facts will come to light 

 as they are progressively cultivated by man. 



In the State of New York, along the base of the Helderberg 

 Mountains, where the Clinton and Niagara sections and the Onon- 

 daga-Salt group are very thin, the Oneida Conglomerate is absent, 

 and the Hudson-River rocks rise to within a few feet of Tentaculite 

 (Waterlime) Limestone. In the south part of Herkimer County 

 (central New York) the shales of the Hudson-River rocks are sepa- 

 rated from the sandstones and ore-beds of the Clinton group only by 

 some thin strata of Oneida Conglomerate (Hall, Pal. ii.). 



From where the Niagara group ends eastwards (at Little Falls) 

 the Onondaga Salt group rests on the Clinton beds ; and still more 

 easterly it reposes on the Frankfort Slate of the Hudson-River rocks, 

 and so continues to within a short distance of the River Hudson. 

 This is an important and extensive example of actual contact of 

 Lower and Upper Silurian, having of course its palaeontological 

 consequences. 



The grey or yellow porous limestone of the same Onondaga-Salt 

 group was met with by Vanuxem at Sharon Springs, overlying 

 Frankfort Slate and underlying the Helderberg series. With these 

 facts before us, we need not be surprised at fourteen fossils having 

 been recognized by some of the ablest palaeontologists of any period 

 as belonging to both Upper and Lower Silurian. 



