190 The Ohio Journal of Science [Vol. XVII, No. 6, 



At Hillsboro, Ohio, the West Union formation is separable 

 into two members containing a very different fauna. The 

 upper, or Lilley member, exposed at various localities on 

 Lilley Hill, consists of about twenty feet of massive limestone 

 usually overlaid by two or three feet of clay. It has been 

 identified with certainty so far only in the vicinity of Hillsboro. 

 The lower, or Bisher member, typically exposed northeast of 

 the Bisher dam, contains a very characteristic fossil horizon 

 about nine feet above its base, and several other layers, less 

 abundantly fossiliferous occur between twelve and twenty feet 

 farther up. This lower horizon appears to have a much wider 

 horizontal extension. Along the creek, half a mile west of 

 Port William, about seven miles north of Wilmington, the total 

 thickness of West Union formation is less than five feet. It 

 immediately underlies the Cedarville dolomite, and appears to 

 represent the fossil horizon which at Hillsboro occurs nine feet 

 above the base of the Bisher member. Farther northward, the 

 West Union formation appears to be entirely absent. 



In the vicinity of Hillsboro, Ohio, the Crab Orchard forma- 

 tion consists of 62 feet of clay underlaid by the Dayton lime- 

 stone, 3.5 feet thick. The latter contains Pentamerus oblongus 

 at several localities: Two miles west of Peebles, two miles 

 south of Bellbrook, and near Dayton (Ohio Geol. Survey, 1870, 

 p. 280). This Dayton limestone may correspond approx- 

 imately to the Walcott limestone division of the Clinton 

 formation in Niagaran section at Rochester, New York. 



In the upper part of the Crab Orchard clay shale, in northern 

 Kentucky and southern Ohio, thin layers of indurated shale 

 occur which contain Liocalymene clintoni, Beyrichia lata- 

 triplicata, and other fossils. Fossils have been found at this 

 horizon in the exposures a mile west of Peebles, Ohio, and the 

 horizon probably may be traced as far northward as Hillsboro, 

 Ohio. It evidently corresponds to the typical Clinton of New 

 York, as exposed at Clinton, in that state. 



North of Hillsboro, Ohio, the Crab Orchard clay shale 

 section changes rapidly in character. No equivalent to the 

 upper fossiliferous part of the Crab Orchard clay shale may be 

 recognized at Leesburg, 11 miles northward. Here the clay is 

 represented by a more or less indurated and imbedded rock 

 which may soften up under the influences of weathering, but 



