LIMESTONES OF WESTERN TENNESSEE 687 



Rhipidomella resembling Rhipidomella oblata. Two species of 

 Spirifer occur which are related apparently to Spirifer iiniciis 

 and Spirifer arrectus. The typical Upper Oriskany, characteristic 

 of the Oriskany sandstone of the Appalachian region, does not 

 occur, but a part of the Camden chert appears to belong to a 

 higher horizon at least than at first supposed. A single specimen 

 of Edriocri?ius was found. 



The same species of Edriocrhuis occurs near the western end 

 of the exposures along the Cumberland River, west of Cumber- 

 land City; on the eastern side of the railroad, a quarter of a mile 

 south of the home of John Broadus ; and on the rocky face of 

 the hill southeast of the home of Christopher Schmidt, about a 

 mile south of the home of Dr. Scott. At the western end of the 

 exposures along the Cumberland River Professor Safford identified 

 the top of the limestone section as belonging to the Camden 

 horizon. The writer was not able to verify this in the short time 

 at his command. No specimens of the species of Edriocriiius in 

 question were found in the undoubted Linden bed exposures 

 farther southward, but the genus is known to occur also in the 

 Helderbergian elsewhere, although the species in question may 

 have a more limited range. 



13. The Onondaga limesto?ie. — On the western flank of the 

 Cincinnati geanticline, along the Harpeth River, between Newsom 

 and the bridge west of Pegram, the Silurian is directly overlaid 

 by a thin bed of Devonian limestone,' varying in thickness from 

 12 feet at the west to 3 feet at the most eastern point of outcrop. 

 West of Pegram, at the bridge, it rests upon the soft clay forming 

 the lowest part of the Brownsport bed. At Newsom, at the most 

 eastern point of outcrop, it is underlaid by the equivalent of the 

 Lego bed, 32 feet thick. Nucleocrijius {^Olivanites) vernetiili^ is a 

 characteristic species. Stroplieodoiita demissa, Stroplieodonta perplana 

 Rhipidomella penelope, and Nucleospira concinna are also found. 

 This white and comparatively pure limestone is overlaid by a 

 darker and moresandy limestone containing small grains or concre- 

 tions of some black substance, similar to the black particles found 



'Silurian and Devonian limestones of Tennessee and Kentucky, Bull. Geol. Soc. 

 Anier., Vol. XII, 1901. 



