PROCEEDINGS OF THE OOLUMBUS MEETING 



The next paper was entitled : 



SILURIAN-DEVONIAN BOUNDARY IN NORTH AMERICA 

 15Y HENRY S. WILLIAMS 



The paper was presented only by abstract, and was discussed by J. M. 

 Clarke and J. F. Whiteaves (a former Fellow of the Society). 



The following paper was then read : 



THE SECTION AT SCHOHARIE, NEW YORK 

 BY JOHN J. STEVENSON. 



[A bstract] 



The village of Schoharie, 35 miles southwest from Albany, is very near the 

 mouth of Schoharie valley, an indentation of the Helderberg mountains. The 

 section in the hills, bounding the valley at that place, extends from the Hudson 

 to the Hamilton, and is so well exposed in detail as to afford means for comparison 

 with sections obtained in southern Pennsylvania, as well as in Virginia, within 

 the Appalachian region. 



No trace of either Oneida or Medina appears at Schoharie, and the thin eastern 

 representative of the Clinton rests on the Hudson. In this respect the condition 

 differs from that in the Shawangunk mountains -the southeasterly border of the 

 Catskill area — where the Oneida is a massive conglomerate. The contrast with 

 the southern sections is striking. In those the Hudson passes very gradually into 

 the red or lower Medina, as is seen well in southern Pennsylvania and still better 

 in southwestern Virginia. Rhyncotrema capax, Rqfinesquina alternata, Plectambonites 

 sericea, Ambonychia radiata, Avicula emacerata, and some other forms continue into 

 the red Medina, even to within 100 feet of the white Medina in the more southern 

 localities. 



The Niagara is represented at Schoharie by the Coralline limestone, about 6 

 feet thick, containing great numbers of Favosites niagarensis, Stromatopora coiicen- 

 trica, and a few mollusks. This dark brown limestone is succeeded by the Water- 

 lime, in all about 40 feet thick, whose lowest portion, about 6 feet thick, is the 

 well-known "Cement rock" of Schoharie and Ulster counties. This rock is of 

 lighter color and very different composition. In a great part of tlie Appalachian 

 region the Salina shales, often several hundred feet thick, are seen between these 

 rocks, but in the Schoharie area the limestones are in contact and the change in 

 conditions was so slight that the Favosites and other forms continued into the 

 Waterlime, the coral occurring so abundantly in some places as to render the 

 " Cement rock " worthless. The higher part of the Waterlime is flaggy and much 

 of it thinly laminated, while the rock becomes more calcareous. 



The passage to Helderberg is marked physically by a complete change in color, the 

 Waterlime being light gray and the Tentaculite, the lowest division of the Helder- 

 berg, very dark blue; yet Spin/era vanuxemi and Leperditia alia, two forms charac- 

 terizing the Tentaculite throughout, occur in the thicker beds of the Waterlime. 



The successive divisions of the Helderberg, Tentaculite, Lower Pentamerus, Del- 



