24 UNIVERSITY OF MISSOURI BULLETIN 



Conditions of sedimentation were almost uniform while 

 the Ohio shales were being deposited west of Norwalk, but east 

 of this place the Chagrin enters as a wedge with the thin edge 

 to the west. Its calcareous and arenaceous nature indicates 

 shore conditions to the east. 



The Olentangy shale varies in the well data from 110 feet 

 to 147 feet in thickness. The Prout limestone member is absent 

 in the vicinity of Oberlin but is present just west of Huron. 



In the upper two or three hundred feet of the shales cone 

 in cone concretions are abundant and in the lower hundred feet 

 large concretions made up, for the most part, of the shale itself 

 are common. The fish remains from the lower shales usually 

 come from the concretions and those from the upper shales 

 frequently do. Invertebrate fossils rarely occur in concretions 

 except at the contact of the Ohio shales with the overlying 

 Bedford where the concretions are of clay ironstone. 



FOSSIL HORIZONS 



The writer has collected fossils from twelve horizons in 

 the Ohio shales and they probably occur at many other levels. 

 The lowest horizon is at the contact of the shales with the 

 Prout limestone and most of the fossils are in the limestone. 

 Collections have been made from only one locality, about two 

 miles west of Huron, Ohio, along the Lake Shore tracks. Several 

 species of typical Olentangy invertebrates, two or three species 

 of dinichthyids, an Aspidichthys plate, and teeth of two species 

 of shark came from this place. The rock is highly pyritized and 

 the fossils come out with great difficulty. 



The dinichthyids are the oldest from Ohio except D. 

 precursor from the Corniferous. The remains consist of part 

 of a small dorsal plate, fragments of plates and fin rays, and the 

 mandible described in this paper as Dinichthys subgracilis. All 

 of the remains had been washed about by the waves before 

 fossilisation and are more or less worn. 



About twenty feet from the bottom there is a thin bed of 

 shale that contains numerous specimens of Lingula spatulatus . 



