536 Contributions to Invertebrate Palaeontology. 



become thicker and more calcareous, and their surfaces are covered 

 willi 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, rejjresenting the Columbus quarries, includ- 

 ing the coral beds and those containing the large cephalopods. 

 (Lower Corniferous of the Ohio Geol. Kept.) 



No. 2, a thin layer of limestone, four to six inches thick densely 

 filled with teeth, plates and bones of fishes, locally known as the 

 "Bone-bed." 



No. 3, al)0ut thirty feet of thin-bedded shaly limestone, the 

 "Delaware bed" of Prof. Orton. The upi)er i)art of this is sup- 

 posed to represent the beds of similar character at Delaware, Ohio, 

 which contain the large fish-remains. 



No. 4, about fifttsen feet of bluish, somewhat marly shales, the 

 " Olentangy shales" of N. H. Winehell. This is followed above by 

 the Huron shales, the suppos(>d etjuivalents of the Genesee slates 

 and Portage shales of New York. 



Near the lower part of No. 3, only a few feet above the "Bone- 

 bed," occurs the dark brown shale in (luestion, with the peculiar 

 fossils, which I have no hesitation in pronouncing the equivalent of 

 the Marcellus shales of New York. Admitting this — and thqre 

 certainly appears to be no alternative — the rocks found above this 

 limit should represent the Hamilton group of the New York sys- 

 tem ; and we ought to find some fossils here, characteristic of that 

 formation, which would not pass below this line. To ascertain if 

 this was so, I requested Mr. Edward Hyatt, who has collected care- 

 fully the fossils around Columbus, to furnish me a list' of the species 

 known, with their horizons indicated; and also requested the use 

 of specimens of species not known to occur below the horizon of 

 the " Bone-bed," that being the most easily recognized limit, and 

 Ihe one most genernlly studied in connection with the vertical dis- 

 tribution. Contrary to my expectations, the species yet known not 



• These lists will be found appended at the end of the present article. 



