51 S GEOLOGY OF OHIO. 



grains formed of bryozoan remains, broken and rounded by the more or 

 less strong currents of the Clinton sea of this region. Sometimes only 

 the original cell walls of the bryozoans are thus replaced, at other 

 times only the original lime cement filling the cells has been altered, or 

 again, both may have been transformed into an iron ore. 



The Clinton varies between 10—30 feet in thickness, though sections 

 of greater thickness are quoted in the reports of the Ohio Survey. At 

 its base the Clinton is often massive, with the fossil material so commin- 

 uted as to be unidentifiable. The coarser frondose bryozoans are however 

 often still preserved. Towards it upper portion, thin blue clay layers are 

 not infrequent in places and both the limestones and blue clay are then 

 usualty filled with fossils. At the very top of the Clinton the blue clay 

 contains not infrequently fossils of Niagara types, not found, at least in 

 as typical a form, in the limestones beneath; some of these are Orthis 

 hybrida, Or. his elegautula, Eichwaldia reticulata, and Callopora e/egau.zila, 



Immediately over the Clinton limestone at Huffman's quarry south 

 of the Dayton asylum, to a much lesser degree in the quarry at the 

 northern edge of Beavertowu, more typical in the quarries along the 

 Carrollton road southwest of the Soldiers' Home — occurs a greenish mas- 

 sive rock, with conchoidal fracture, not exceeding fifteen inches in thick- 

 ness at the most typical exposure: Huffman's quarry. This, formerly 

 called the Beavertown marl, contains a number of small fossils, peculiar 

 to this horizon, and a number of other fossils of upper Clinton type. 

 The fauna of this marl is in part also represented in the ferriferous upper 

 Clinton at Todd's Fork near Wilmington, so that the marl when present 

 is regarded as the close of the Clinton in Ohio. 



Immediate above the Clinton, or the marl when the latter is present, 

 lies in many places a firm white compact massive limestone divided by 

 partings at various intervals, often quite constant for long distances. This 

 is the Dayton limestone. South of Dayton it locally sometimes shows 

 fossils on the lower surface of the bottom layer, of such types as are known 

 from the Clinton. It contains few fossils, but persons walking the streets of 

 of Dayton and frequenting the stone yards will have noticed occasionally 

 Favosites and Orthoceras, rarely Syringopora, coarse gasteropods, very 

 rarely Ha. ysiles, Strombodes, and Prof. Orton recently found an Atrypa 

 related to A. reticularis. In this relation a quarry in the Dayton limesto e, 

 on the east side of the Bellbrook road, half a mile south of its junction with 

 the Beavertown road at the Presbyterian church, or five and a half miles 

 south of Dayton, proved very interesting. Here eight inches of drab, 

 dolomitic, poor limestone, often- divided into two courses, was underlaid 

 b}" sixteen inches of good solid Dayton limestone, forming a single 

 course, and filled with crinoid beads and stems, which were partially 

 visible on freshly broken surfaces but which showed in considerable quan- 

 tities over weathered surfaces, giving one the idea that the Dayton lime- 

 stone here was a great mass of encrinital material roughly jumbled to- 



