1148 NEW YORK STATE MUSEUM 



the " Ribbon limestone " of some writers. Just below this rib- 

 boned series there is usually a thin bed of Stromatopora which 

 characterizes this horizon. 



This is the true Stromatopora bed of the Manlius, and it ap- 

 pears to characterize this limestone throughout its extent in New 

 York and always in the position as above given. 



Northward from East Kingston the Wilbur limestone is mostly 

 obscured. There is an exposure near Glasco, but from this point 

 it is absent till West Camp is reached, where it is exposed in both 

 limbs of a syncline which extends from West Camp to Oatskill. 

 The Wilbur limestone about West Camp is 3 feet thick, and out- 

 side of its corals Leptaena rhomb oidalis Wilck. is 

 the abundant fossil. Atrypa reticularis Linn, also 

 occurs, but not so abundantly. The presence of the Wilbur beds 

 far north of West Camp has not been established. There are 

 corals at the base of the Rondout and on the Lower Siluric shales 

 at Catskill, but they are considered as belonging to the Cobleskill. 



Results somewhat similar to those which I have obtained rela- 

 tive to the stratigraphic relations of the cement beds at Rondout 

 have been already expressed by the Hon. J. G. Lindsley 1 in a 

 paper read before the Poughkeepsie Society of Natural Science in 

 1870. While the correlation of the cement beds at Rondout as 

 given by Lindsley, differs essentially from that of the writer, 

 it serves to show nevertheless that the cement beds at Rondout 

 have before been considered as belonging to different ages, and 

 this opinion is expressed by one who, as superintendent of the 

 Newark Lime & Cement Co., was familiar with the section, and 

 to whom the proper relations of the cement beds were of prime 

 importance. The following quotation from the paper referred 

 to above will clearly express the views held by Lindsley. In re- 

 ferring to quarries at Rondout, he says: 



In these quarries we find lying directly upon the slates, [=L. 

 Siluric] two layers of coralline [= Wilbur] limestone, the whole 

 thickness of which varies from 6 feet to nearly 8 feet. 



This coralline iimestone is admitted by all geologists of the 

 present time to belong to the Niagara epoch, being the small be- 

 ginning of those rocks here at the east, which, increasing in thick- 

 ness, assume such proportions in the western part of the State. 



1 See Poughkeepsie Soc. Nat. Sci. Proc. 1879. p.44-48. 



