ItEPORT OF THE STATE PALEONTOLOGIST 1902 114'J 



Feet Inches 



The thicknesses by formations are as follows : 



The Manlius '. . 37 6 



The Rondout 23 9 



The Cobleskill 7 



The Salina, including basal limestone 16 11 



I have already, in a previous paragraph, called attention to 

 the fact that the position of the " Coralline " limestone at Scho- 

 harie, as determined by Messrs Ulrich and Schuchert, is said to 

 have been based on the section at Rondout N. Y. In making 

 this determination, however, these distinguished workers in 

 paleontology followed Hall's correlation of this " Coralline " bed 

 as the equivalent of the Cobleskill, or " Coralline," of Schoharie 

 county, an obvious error now that it is known that in Ulster 

 county the Cobleskill belongs to a higher horizon than the so 

 called " Coralline ", and consequently the " Coralline " of the 

 Hudson river valley really belongs to an earlier age. 



Starting from the type locality of the Cobleskill in Schoharie 

 county, where its stratigraphic relations to the overlying form- 

 ations are accurately known, the Manlius limestone can be traced 

 continuously across the Helderberg and into Ulster county. In 

 a like manner, the Rondout at the base of the Manlius can be 

 traced, but it is not always so conspicuous, and specially in the 

 Helderberg it has become very thin, still in Albany county at 

 Altamont, Indian Ladder, New Salem and South Bethlehem it 

 can be observed, and, since the Cobleskill and the Salina have 

 thinned out, it rests directly on the Lorraine shales. Similar 

 stratigraphic conditions exist in the vicinity of Catskill, Greene 

 co., and southward from this place the Rondout becomes better 

 developed, and good exposures are seen just north of West Camp 

 in the cut of the West Shore Railroad. 



In Schoharie county the basal portion of the Rondout lying 

 directly on the Cobleskill is burned for " hydraulic " cement, but 

 in passing eastward over the Helderberg this cement bed thins 

 out and is wanting for many miles. It comes in again before 

 Ulster county is reached, and here, as in Schoharie county, it 

 represents the basal portion of the Rondout as here denned. 

 Throughout Ulster county this basal portion of the Rondout is 



