432 GEOLOGY OF OHIO. 



NOTE ON THE MARCELLUS SHALE AND OTHER MEMBERS 



OF THE HAMILTON GROUP IN OHIO. AS DETERMINED 



FROM PAL^EONTOLOGICAL EVIDENCE. 



During the early summer of 1878, President Edward Ortou wrote, 

 asking if I could spend a few days with him in central and southern 

 Ohio, in an effort to ascertain from palaeontological evidence, the true 

 horizon of certain layers of rock which had been somewhat of a difficulty 

 to him; and in the month of August I spent several days with him for 

 that purpose. While making these somewhat hurried observations at a 

 locality about six miles N. W. of Columbus, in Perry township, on the 

 .east bank of the Scioto river, we accidentally discovered a thin bed of 

 dark brown shale, somewhat fissile and bituminous in character, in what 

 Prof. Orton had considered as a representative of the Delaware lime- 

 stone of Delaware, Ohio. The peculiar texture of the shales, occurring 

 where I had expected only a light-colored limestone, excited my interest; 

 and after a few minutes' examination, I discovered that they contain 

 numerous flattened shells of Leiorhynchus limilaris, Vanuxem. I also 

 obtained from them two specimens of Discina minuta, and examples of 

 Lingula Manni Hall; the two former being well-known and characteristic 

 forms of the Marcellus shales of New York. On examination, we found 

 that these shells, especially the Leiorhynchus, extended through a thick- 

 ness of several feet of the rock, and that the peculiar bituminous char- 

 acter of the shale accompanied them, but with intercalations of thin layers 

 of less bituminous and light-colored limestones. Subsequently, at a point 

 nearly opposite Dublin, Ohio, some miles north of the above-mentioned 

 locality, the same shale was again recognized in a corresponding horizon, 

 accompanied by the same species, the Leiorhynchus being quite numerous. 

 At a subsequent visit, Mr. Edward Hyatt obtained Discina Lode nsisHaW. 

 another New York Marcellus species. At this second locality, immedi- 

 ately above the shale, and while the limestone layers retain much of the 

 bituminous character, the layers become thicker and more calcareous, 

 and their surfaces are covered with the shells of Spirifera gregaria Clapp, 

 and Tentaculites scalariformis Hall, both of which are likewise common 

 in the blue limestone layers at Delaware, Ohio. 



A section of the rocks at the first-mentioned locality, six miles N. 

 ' W. of Columbus, on the east bank of the Scioto, subsequently furnished 

 by Prof. Orton, is as follows: 



The lower bed, No. 1 of section, is a heavy-bedded limestone about 

 thirty feet thick, representing the Columbus quarries, including the coral 

 beds and those containing the large cephalopods. (Lower Corniferous 

 of the Ohio Geol. Rept.) 



