at the Falls of the Ohio. 



179 



It should be remembered that the facts above stated, 

 aud the fossils enumerated, have been derived from a sin- 

 gle locality — the Falls of the Ohio river. Elsewhere, in 

 Kentucky and Indiana, the same conditions exist and the 

 same species of fossils are known. In the state of Ohio 

 similar conditions may be inferred, from the fact that cer- 

 tain species of known Hamilton fossils are published in 

 the Ohio Geological Reports as from the Corniferous 

 group. 



In the state of Wisconsin, the magnesian limestones of 

 the Humboldt river, near Milwaukee, are charged with 

 characteristic Hamilton fossils, and doubtless represent 

 the hydraulic limestone and superincumbent beds at the 

 Falls of the Ohio. I shall, at some future time, give a 

 list of species which I have recognized in that locality 

 during a former geological survey of the state. In" the 

 states of Illinois and Iowa, the Hamilton group is every- 

 where partially or entirely represented by a limestone, 

 and the term " Hamilton limestone " has been used in the 

 geological reports of the former state. In those portions 

 of the country where the Upper Helderberg limestone is 

 not known as a member of the series, there seems less diffi- 

 culty in recognizing the age and character of the Hamil- 

 ton limestones. It is in those localities where the Upper 

 Helderberg limestone is well developed, and where the 

 superincumbent beds are conformable, that they are likely 

 to be regarded as a component part of the formation, and 

 their fossils grouped together in accordance with this 

 view. 



The number of species of the hydraulic and encrinital 

 limestones which are common to these beds and the Ham- 

 ilton group of New York, as shown in the list above pre- 

 sented, certainly offers very strong evidence in support of 

 the view which I am compelled to take, that they are the 



