140 



PALEONTOLOGY OF NEW YORK. 



limestone (the great coral reef, comprising the Onondaga and Corniferous lime- 

 stones of the New York system) seems to have been originally unbroken, at 

 least from the valley of the Hudson nearly and perhaps quite to the line of the 

 present valley of the Mississippi. It is traceable in unbroken continuance from 

 the Hudson to the Niagara rivers, and through Canada west to Lake Huron, and 

 thence into Michigan ; while in a southwesterly direction are the outcrops on 

 the two sides of the Cincinnati axis, extending through Ohio and Indiana, and 

 thence into Kentucky, where it gradually thins out. During the formation 

 of this remarkably extensive coral reef, there could have been no great change 

 in the conditions of the ocean ; for not only do these corals indicate an undis- 

 turbed and luxuriant growth, but the same genera and the same species prevail 

 over a large part of the above area. It is only in tlie superjacent beds that 

 we may look for changed conditions, which have given origin to the different 

 terms used to designate the subdivisions of the formation in different parts of 

 the country. 



In New York we have the following members of the series, between the 

 Marcellus shale and Oriskany sandstone : 



1. Marcellus shale. 



2. Limestone with Ichthyic remains (bone 

 bed) 



3. Cherty beds, with species of Loxonema, 

 Pleurotomaria, Bellerophon, etc. .  



4. Corniferous limestone 



5. Onondaga limestone (the great coral 

 bearing limestone) 



6. Schoharie grit. 



7. Oriskany sandstone. 



Upper Helderberg 

 group. 



The Corniferous 

 limestone of 

 Eaton.* 



• In the arrangement of Prof. Eaton, all the limestone formation between the Sehoharie grit and Mar- 

 cellus shale was termed " Corniferous linn-stone " — no subdivisions being recognized. In the reports On the 

 Geological Survey of New York, the subdivision into Onondaga and Corniferous limestones was made tor the 

 convenience of reference, and on account of the character of the prevailing fossils in the two members. 

 Farther investigation has shown the existence of a peculiar Chorty bed Containing characteristic fossils, and 

 i a Calcareous bed with remains of fishes ; l>oth of which are distinct from the Onondaga and Corniferous 



