GEOLOGY OF THE NEW YORK CITY AQUEDUCT 



43 



(i6) Coeymans limestone. Heavy bedded, dark gray, argillace- 

 ous and flinty limestone. The characteristic features for field 

 identification are (a) abundant chert nodules, {h) the occurrence of 

 coral reef structure and heads of corals, Favosites helder- 



Fig. 



S S pli r i f e r'^Im acropleu rja (Conrad), the most characteristic index fossil 

 of the New Scotland beds in the Rondout region 



e a t a and 



b e r g i a . The brachiopods Sieberella ga 

 Atrypa reticularis are very common. 



This formation has a thickness of about 80 feet and is rather 

 distinctly separated from the underlying Manlius. The Coeymans 

 is considered the base of the Devonic system of New York. 



It is 



Fig. 6 



Sieberella galeata (Dalmaa), the most reliable 

 Coeymans limestone of the Rondout region 



index fossil of the 



perfectly conformable upon the underlying series and it is evident 

 that in this region there was no important break in the progress of 

 deposition. 



e Siluric strata. (17) Manlius limestone. Lime mud rock, fine 

 textured, dense, with plainly marked sedimentation lines, gray to 

 dark gray color. The most characteristic features in the field are 

 {a) fine texture, (Jj) sedimentation lines, as if laid down in quiet 

 waters as a lime mud, (c) solution joints sometimes enlarged to 



