of the Devonian of Western Tennessee. 739 



largest deposit of an oolitic iron-ore to be found above 

 the Clinton. These beds yielded the ore which was mined 

 before the Civil War at a locality about 2 miles southwest 

 of Clifton. The cross-bedding which characterizes this 

 member bears evidence that the oolite was deposited in 

 shallow water. Fossils occur throughout it and are 

 especially common in a band of muddy, cherty limestone 

 near the middle. The fauna, however, closely resembles 

 that of the Ross member below, fifteen of its eighteen 

 species being common to the latter. The chief differ- 

 ences to be noted are the presence here of Eatonia 

 eminens and the absence of Camarocrinus and the 

 Scyphocrini which characterize the lower member. 



The Ross limestone member was first described by 

 Poerste (1903). It is a dense, fine-grained, siliceous or 

 cherty limestone of dark gray color, disposed in thin 

 layers from 2 to 5 inches thick. Although very hard and 

 compact when fresh, it weathers to a soft, porous, shaly 

 sandstone of rusty brown color. Its most characteristic 

 fossils are the Camarocrini and Scyphocrinus pyburnen- 

 sis and S. pratteni. Because of the abundance of the 

 crinoid bulbs Foerste called it the " Camarocrinus or 

 Ross limestone." Other fossils occur in more or less 

 abundance, the more important of which are listed 

 beyond (page 741). 



For a distance of 20 or 25 miles to the south and south- 

 west of Olive Hill, only the lower or Ross limestone mem- 

 ber has escaped later erosion, but at Pyburns Bluff on the 

 Tennessee River, and at a bluff on Dry Creek near the 

 southern line of the state, thick sections of the Olive Hill 

 formation are again exposed. Here, however, the sub- 

 divisions seen at Olive Hill cannot be clearly recognized. 

 In the section at Pyburns the formation is between 80 and 

 100 feet thick, and its base is below drainage. Here it 

 consists of dense, fine-grained, impure and cherty lime- 

 stone throughout. The lower portion is characterized by 

 Camarocrini, but this fossil is absent in the upper por- 

 tion.^ On this faunal basis Foerste subdivided the sec- 

 tion into the Ross limestone below and the Pyburn 

 limestone above. The Ross here agrees in faunal and 

 physical characters with that at Olive Hill and with the 

 intervening sections as well. The Pyburn holds, more or 

 less, the stratigraphic position of the Bear Branch mem- 

 ber at Olive Hill, though its lithologic characters are 



