NEW YORK. 



8? 



be identified by characteristic fossils, as well as by their superposition and well marked lithological 

 appearances. When the State geological survey was made, forty years ago, these extensive de- 

 posits of slate rocks were called Hudson River slates. Afterwards, in accordance with the Canada 

 survey, they were called the Quebec group, by which they are yet designated as a general title, for 



