348 CHARLES S. PROSSER 



same general period of deposition as the Brassfield limestone." 1 

 The Sexton Creek limestone is the upper formation of the Alexan- 

 drian series, named and described by Professor Savage, 2 a series 

 that in Illinois and Missouri contains all the formations between the 

 Richmond-Maquoketa formation, at the top of the Cincinnatian 

 series, and the base of the Niagaran series. 



Since the above was written, advance pages of a work on 

 Historical Geology by Professor Schuchert have been received in 

 which the following correlation appears: 



Lower Silurian (Medina, Cataract, and Brassfield formations, 

 or Oswegan \Becsie limestone. 3 



OTHER SECTIONS OF WESTERN OHIO 



Sections farther up the Stillwater River toward Covington show 

 the middle and upper parts of the section exposed along Ludlow 

 Creek, while those in Covington carry the general section still 

 higher. Sections farther west, near Lewisburg and New Paris, 

 agree essentially with those of the Stillwater Valley. 



Sections in and near Covington. — About two miles south of 

 Covington is the Jackson Stone Co. quarry, near the Stillwater 

 River, on the Charles H. Jackson farm. It is easily reached by the 

 Piqua, Covington, and Dayton trolley line, leaving the car at stop 45, 

 which has the name of Sugar Grove. The section given below is 

 of the eastern wall of the quarry, the top of it near the engine 

 house, a short distance southwest of the crusher. 



Section of the Jackson Stone Co. Quarry 



Thickness ThS^ss 



No. Feet Inches Feet Inches 



22. Cedarville dolomite. — Buff, mostly porous, crys- 

 talline dolomite, with Pentamerus oblongns 

 Sowerby common all through the outcrop. 

 Zone at base with large number of specimens 

 of Pentamerus oblongus Sowerby as well as 

 Favosites niagarensis Hall 3 8 109 9 



1 Illinois State Geological Survey, Bull. 23 (1913), p. 33. 



2 American Journal of Science, 4th Ser., XXV (1908), 434, 443; Illinois State 

 Geological Survey, Bull. 23, pp. 14, 15. 



* A Text-book of Geology, Part II, Historical Geology (1915), p. 661. 



