52 LTE J OOLINALES OLN GAR OWE OG NA 
time, and it seems also safe to say that it not only marks the date but 
furnishes the producing cause of the change in the formation that then took 
place. The Medina shales may be referred to sediments that settled in seas, 
disturbed by igneous agencies—the long continued life of the preceding 
periods being exterminated in this region by the shallowing waters, as the 
low mountain chain emerges.” : 
The change in formation, to which reference is made above, 
is that from the alternating limestones and clays of the Cincin- 
Thrrosad curves consider 
ally. The original drawings were 
ost and replaced from memory. 
2) 
wy 
4 
aQ 
Ly 
ty 
A 
Sketch maps of localities referred to in this article. 
nati group to the shales of the Medina. Volcanic disturbances 
sufficient to keep the sediment of the sea in commotion, are 
hardly necessary to account for the change in the lithological 
character of the two formations. 
Former observations by the writer, based upon Professor Orton's 
material.mSome years ago Professor Orton kindly placed at the 
disposal of the writer the pieces of conglomerate which had 
come from the original locality near Belfast. At that time it 
was noticed that the fossils contained in the cement among the 
pebbles were all of Clinton age, and not a single species of 
Cincinnati group affinities was found. Even in the case of 
Orthis lynx it was the Clinton form, and not one of the Cin- 
