Clarke — Oneonta, Ithaca and Portage Groups. 



45 



north of Marathon (Station XI); and near Lisle, Broome county (Station 

 XII). 



In their upper portion these beds become distinctly more arenaceous, the 

 fossiliferous horizons more widely separated. The difficulty of making a 

 well-defined line of distinction between these upper beds and the formations 

 of the Chemung group has already been mentioned. So far south as the 

 formations have been traced by me in the Tioughnioga valley, no satisfactory 

 evidence of a Chemung fauna has been observed. The fauna found at Lisle 

 indicates the presence of the Ithaca fauna, and my observations have not 

 extended south of this point. Professor Prosser reports Dictyopli yton and 

 other Chemung fossils at Whitney's Point, three miles below. 



Oneonta Group. 



The attempt has been made to represent upon the map the relation of 

 this group to the Ithaca group as explained in the introductory pages of this 

 paper. On the Chenango river the red and green shales and sands rest upon 

 beds which rarely contain Spwifer mesastriaMs. Westward these beds 

 disappear by thinning, dovetailed into the edges of the upper Ithaca beds, 

 and at Greene we doubtless have actual superposition of a Chemung fauna 

 upon the Oneonta beds. 



