64 ON PTEEASPIDIAN PISH EST TJPPEE SILTJEIAN OE NOKTH AMERICA. 



that must be assumed to exist in the European series of deposits if 

 the author's stratigraphical views were correct. 



Mr. HoPEiKSON said that there could hardly be a gap between 

 the Wenlock and Ludlow series in this country, seeing that so 

 many species of Graptolites, and also other fossils, passed uninter- 

 ruptedly from the highest beds of one into the lowest of the other, 

 that, from a palseontological point of view, it was difficult to draw 

 the line between them. 



Mr. Blaneoed said that Professor Claypole did not assert that any 

 break occurred between the Wenlock and Ludlow, but apparently 

 the stages were more numerous in America than on this side of the 

 Atlantic. He also indicated, from his own experience, how difficult 

 it often is to decide whether a break occurs between different beds. 



