io6 Bulletin 12 234 



j^ . (5. Black bituminous schists. 



•^" ' 1 4- Shelly limestone and coralline limestone. 



Silurian S3-stem. f 3. Silicious or magnesian limestone (Cliff 

 (Superior.) ( limestone). 



Silurian Sj^stem. f 2. Blue limestones and marl. 

 (Inferior.) | i. Compadl limestone. 



Regarding the correlation of the Devonian of Indiana and 

 Kentucky with the New York Devonian, de Vernueil states that 

 "in the states of Ohio, Indiana and Kentucky it is reduced to 

 the black shists which represent the Genesee slate and to a cal- 

 careous band which represents at once the Corniferous and Onon- 

 daga limestone and the Hamilton group of the state of New 

 York."^^ 



In 1 85 1 Prof. Hall published a paper on the "Parallelism of 

 the Palaeozoic Deposits of the United States and Europe." Hall 

 seems inclined in this paper to accept de Verneuil's view of the 

 age of the Black shale of the west and says "it may be a repre- 

 sentation of the Genesee slate of New York, but holds the place 

 of the Marcellus shale, resting direcftly upon the Corniferous 

 limestone, "t It is apparent from this quotation that Prof. Hall 

 did not recognize any representative of the Hamilton in Indiana 

 and Kentucky at the time it was written. This view he contin- 

 ued to hold for some time. Eleven years later, in speaking of 

 the age of the Goniatite beds at Rockford, Ind., he says: "As 

 the Hamilton group has not been recognized in the south part of 

 Ohio or Indiana, so far as I know, there may yet be room for 

 doubt as to whether this group thins out beneath the Black shale or 

 above it; or, in other words, whether the Black shale of southern 

 Ohio and Indiana, and of Kentucky .and' Tennessee, may be the 

 continuation of the Marcellus shale or the Genesee slate. "^ 



Sidney Lyon and S. A. Casseday seem to have recognized the 

 Hamilton at the Falls of the Ohio as early as 1859; for in referring 

 a crinoid described by them to its geological horizon they state 



*Am. Jour. Sci., vol. 5, 2d ser., 1848, p. 370. 



fReport on the Geology of the Lake Superior Land Distridl, 1851, p. 



307. 



ti5 N. Y. Regents' Report, 1862, p. 81. 



