The Ciftcinnatiau Series and its Brachiopods. 21 



and yellowish shales. Of itself, it is not a distinctive 

 horizon. It is only because of its marked contrast with 

 underlying and overlying members of the McMillan forma- 

 tion, that the Corryville is easily recognized. In the field, 

 it is usually identified by means of its position with relation 

 to other members, or by means of the characteristic bryozoan 

 of the member, C'hiloporclla nicholsoni. The Corryville 

 l)eds are exposed on the higher hills around Cincinnati. 

 Fossils are abundant: Platystrophia lynx is quite large; 

 pelecypods, Anomalodonta and Byssonchia, are plentiful; 

 and the bryozoan, Callopora ramosa, is very abundant and 

 well preserved. 



Mt. Auburn. — The Mt. Auburn is composed of a nodular 

 calcareous shale or shaly limestone, 20 feet thick. The 

 type fossil of this member is the large gerontic form of 

 Platystrophia lynx. This is especially abundant throughout 

 the lower 5 to 12 feet, and may be found throughout the 

 entire member. Other fossils are not abundant. This 

 member is represented at Cincinnati only by its basal 

 part, which is the highest bed-rock on several of the highest 

 hilltops, as at Fairview Heights (Clifton Ave. and McMillan 

 St.), Price Hill, and Westwood. The Mt. Auburn is the 

 highest division of the McMillan, since it is now known that 

 the overlying Arnheim (Warren), which was formerly placed 

 in the Maysville should, because of its faunal relations, be 

 classed as basal Richmond. 



4. Richmond^ — With the exception of the lower strata 

 of the Arnheim, the Richmond formation is not found 

 nearer than about thirty miles to the east, north, and west 

 of Cincinnati. To the south, it is even farther removed, 

 because the center of the Cincinnati anticline is to the 

 south of Cincinnati, in Jessamine Co., Ky. At certain 

 horizons, the Richmond formation resembles the Eden more 



*Nickles: Jour Gin. Soc. Nat. Hist., vol. 20, 1902, p. 83. 



tThe discussion of the Richmond formation is taken largely from Cumings' paper, "The 

 Stratigraphy and Paleontology of the Cincinnati Series in Indiana," Ind. Dept. Geol. 

 Nat. Res., 32nd Ann. Rep., 1907; and Nickles. "Richmond Group in Ohio and Indiana," 

 Amer. Geol. xxxii, 1903, pp. 202-214. 



