BIGSBY PALEOZOIC BASIN OF NEW YORK. 437 



discemibly of fragments of hypogene rocks, such as mica?, felspar, 

 and quartz, — indications of some disturbance. 



2. There is here a sudden and almost total change of fossil life. 

 Not only are nearly all the Silurian fossils extinguished, but we wit- 

 ness the accession of many new genera of invertebrates, and the first 

 appearance of fish and reptiles in North America. 



3. Small but certain indications of terrestrial vegetation are here 

 met with. 



The Devonian system covers about one-third of the State of New 

 York, and especially its central and southern districts. It was pro- 

 bably De Verneuil that first announced its true palaeozoic limits, from 

 having discovered the remains of fish, the Goniatite of Nassau, 

 Murchisonia bilineata, Productus subaculeatus, Athyris concentrica, 

 large Spiriferi, and many other characteristic fossils in the strata 

 beginning with Oriskany Sandstone and ending in Coal-measures. 



The Devonian fossils of this basin, even with the most sanguine 

 expectations of James Hall as to the result of future research, are 

 much fewer than those of the Rhenish provinces and other parts of 

 Europe. 



In Eastern Canada (Gaspe) the Devonian is 7000 feet thick, ac- 

 cording to Sir "William Logan ; but in New York the greatest thick- 

 ness of the Devonian is 4000 feet ; and it thins out west, disappear- 

 ing entirely beyond the Mississipi, where the carboniferous rocks 

 repose on Silurian strata. In Arkansas, more to the south, however, 

 the Devonian (Chemung, Rogers) is in great force again, as well as 

 in Nova Scotia (Dawson), and in Massachusetts, near Boston, as 

 detected by Professor Agassiz. 



The five groups into which I have compressed the twelve sections 

 of the American geologists will now be noticed seriatim, and then 

 the three stages into which, for convenience, I have divided them. 



See Table VII. in the ' Synoptical View,' for the group -relations 

 of the Devonian fossils of New York. 



Groups. 



Oriskany Sandstone, Caudagalli Grit, Schoharie Grit. Group I. 

 — These three beds being, in truth, one deposit, we treat them as 

 such (see ' Synoptical View'). We observe that the Lower Devonian 

 stage begins, like the Lower Silurian and the Upper Devonian, with 

 a sandstone, containing so much disseminated calcareous matter, as, 

 first, to be a calciferous sandstone, terminating upwards abruptly in 

 a limestone, which has received the name of the Onondaga Lime- 

 stone. Lithologically, therefore, the Oriskany Sandstone, with its 

 small subordinates, is clearly separate from all other Devonian 

 deposits. 



The facies of the fossils of this group is Devonian, and they are 

 often of large size, — a Devonian characteristic ; thirteen are original 

 and six typical. It contains two Silurian Brachiopoda. Its five 

 Spiriferi are distinctly Devonian, as are its Cyrtoceras (Eifel) and 

 the Pleurorhynchus (?) . Schoharie Grit has yielded more than one 



