THE CINCINNATI GROUP 33 



exposed in the Cincinnati hills. They are also known as the 

 Platystrophia lynx beds, on account of the great abundance of a 

 characteristic variety of this fossil which attains a large size and 

 has a short hinge line. Both the Warren and the Mount Auburn 

 beds are well exposed north of Lebanon, O. The Fairmount beds 

 are well exposed immediately west of the river at Hamilton. 



Mr. J. M. Nickles determined the thickness of the Utica to 

 be 260 feet at Cincinnati, and the thickness of the Lorraine at 

 the same locality as 310 feet. The thickness of the Richmond 

 was stated to be between 200 and 300 feet, the locality not being 

 mentioned. At the more northern exposures in Indiana its 

 thickness appears to be 240 feet, according to measurements by 

 the present writer. 



Judging from exposures in Nelson and Washington counties 

 in central Kentucky, and from outcrops along the Cumberland 

 river in southern Kentucky, the Lorraine becomes thinner south- 

 ward. The rate of thinning, however, is much less than that of 

 the Richmond in the same distance. In Marion county in central 

 Kentucky the Richmond does not exceed 35 feet. Along Fish- 

 ing creek, ^ a tributary of the Cumberland river, the Richmond 

 is at least 27 feet thick. 



B. THE CINCINNATI GROUP IN THE TENNESSEE RIVER VALLEY. 



The Utica, Lorraine, and Richmond groups may be identified 

 also in Southwestern Tennessee, along the Tennessee river and 

 some of its tributaries. 



I. The Saltillo Limestone. — The Utica consists of fine-grained, 

 gray or bluish-gray limestone layers, from 2 to 5 inches thick, 

 interbedded with equal thicknesses of shaly clay. At Clifton, 

 on the Tennessee river, attempts were made before the war to 

 burn it into a cement; it is, therefore, referred to by Professor 

 Safford^ as the hydraulic limestone. He estimates its thickness 

 at Clifton as 70 feet down to low water, its base not being 

 exposed at any point in the Tennessee river valley in western 

 Tennessee. 



•"The Cincinnati Anticline in Southern Kentucky," /4/«. GeoL, December, 1902. 

 ^ Geology of Tennessee., 1869. 



