THE LOUISVILLE LIMESTONES. 139 



THE LOUISVILLE LIMESTONES. 



NOTE ON THE HYDRAULIC BEDS AND ASSOCIATED LIMESTONES AT THE FALLS OF THE OHIO. 



At the Falls of the Ohio and adjacent localities, the lowest beds of the 

 limestone formation are marked by the presence of Halt/sites catenulatus, and 

 for a long time have been locally known as the " Catenipora beds." This 

 Silurian limestone is succeeded by the great coral-bearing Devonian limestone, 

 which is everywhere, in that part of the country, a well defined geological 

 horizon ; and though the higher beds of the formation are distinguished by 

 the presence of other fossils than corals, there is no marked physical change 

 from the base to the upper stratum which is characterized by Spirifera acumi- 

 nata. The whole is more generally recognized by its numerous corals, and 

 the genera Favosites, Michelinia, Zaphrentis, Heliophyllum and Cystiphyllum 

 are prevailing forms* This limestone is succeeded by beds of an argillaceous 

 magnesian limestone, known as the "Hydraulic limestone," which gradually 

 merges above into thin, slaty beds, some of which are highly siliceous, and 

 these are followed by what is known as the " Encrinal limestone ;" the whole 

 terminated above by the black slate. This entire limestone formation above 

 the " Catenipora beds" has been generally, if not universally, recognized as of 

 the age and the western extension of the Upper Helderberg group of New 

 York (representing all that was originally included by Eaton under the 

 designation of Corniferous limestone and Schoharie grit). I have accepted 

 and advocated this view of the age of these formations, which seemed to be 

 sustained by large numbers of identical fossils from the two distant regions; 

 and I believe that their relative age has not, up to the present time, been called 

 in question. 



As might naturally be expected, the subdivisions recognized in the east and 

 in the west do not always coincide, but it is usually quite possible to correlate 

 these different members by a comparison of their fossil contents. The main 



* It was. from (he presence, in this locality, of nnmeroua species of Corals, identical with those of the 

 New York formations, that, in 1841, I recognised these limestones as of the same age. 



