200 Cincinnati Society of Natural History. 



Remarks Suggested hy Recent Observations. 



Since the foregoing observations were written a number of local- 

 ities between Osgood and Charlestown, Indiana, were visited. There 

 certainly was no room for the Medina between the top of the Lower 

 Silurian and the base of the Clinton, or (when the Clinton was absent) 

 the base of the Niagara, at these localities. It has become a certainty 

 therefore that the Medina is absent in Indiana and the western line of 

 counties in Ohio. If present in Ohio and actually outcropping, it 

 can be represented only by the Belfast bed, from Adams to Miami 

 counties. The Belfast bed, however, turns westward into a clayey, 

 less solid rock which at times contains or is overlaid by Lower 

 Silurian fossils. 



In the southwestern exposures of the Upper Silurian in Indiana 

 recently visited, the Clinton never exceeds 3^ feet in thickness, is 

 usually much thinner, and at several localities has been found entirely 

 absent. Observations so far made suggest that the Clinton once 

 extended across the Cincinnati anticlinal axis in southern Ohio, that 

 it thinned out from 30 to 40 feet at the more eastern exposures in 

 Ohio to less than 4 feet at the more western exposures in Indiana, 

 and that at a number of localities in Clark, Ripley, and probably in 

 Fayette counties in Indiana, the Clinton is entirely absent. Numerous 

 pebbles were found at the base of the Clinton at Osgood and at 

 several localities southwest of Versailles, the extreme localities being 

 io miles apart. Evidence is accumulating for the existence of land 

 conditions west of the outcrops of Clinton from Fayette to Clark 

 counties in Indiana. The Clinton, instead of being deposited around 

 an island, the northern end of which extended into Ohio near Cincin- 

 nati, has been deposited against land lying west of the line of out- 

 crops in southern Indiana. 



From the middle of the western side of Fayette county and the 

 eastern side of Union county in Indiana, the Clinton thickens on 

 going northwards. 



The additional observations recently accumulated, and here in 

 part recorded, will form a continuation of the present paper. 



