440 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



grey sandstones, about 150 or 200 feet from the base of this for- 

 mation. 



Borings have been made in these rocks, both in Indiana and Ohio, 

 in search of salt water, and brines have been procured, but Ihey are 

 weak, and have not been able to compete with those situated in the 

 coal-measures. 



Proceeding in the descending order, we now arrive at the bitu- 

 minous, aluminous shale and associated limestones. This group con- 

 sists chiefly of a dark-coloured, schistose, argillaceous deposit, closely 

 resembling the shale of the coal-measures, though somewhat more 

 compact. Beneath it in Indiana and Kentucky are subordinate beds 

 of limestone a few feet in thickness. The lowest of these, as it ap. 

 pears in the bed of the Louisville canal, is argillaceous, and affords 

 a valuable water- cement. Above it, in Floyd county, Indiana, are 

 about two feet of a green ferruginous limestone, of high specific 

 gravity. In the same position, in many places in Tennessee, we find 

 a limestone, which, from its being often remarkably rich in Crinoidea, 

 has been described by Troost under the name of Encrinital limestone. 

 The range and extent of this group are shown on the map, and its geo- 

 logical position is indicated in the diagram. It crops out at the base 

 of the conical-shaped range of hills known in Indiana and Kentucky 

 as the " Knobs." In the base of the hills of the iron region of Mid- 

 dle Tennessee, it is seen both on the northern and on the southern 

 declivity. 



To the east, in Ohio, the thickness of the bituminous shale is 

 greatest, and amounts to from 250 to 300 feet*. In Indiana it is 

 upwards of 100 feet. To the south the bed becomes thinner, in 

 Tennessee seldom exceeding twenty or thirty feet, and in some loca- 

 lities is not more than eight or nine feetf. Occasionally in Tennessee 

 this shale is replaced by indurated slaty clay. To the west it runs 

 out, and in Iowa no vestige of it could be discovered. 



At no locality, either in Indiana, Illinois, Kentucky or Tennessee, 

 have I ever been able to discover any organic remains in the shale, 

 except some slight impressions apparently of seeds or seed-vessels. 

 Neither have the geologists of Ohio there discovered in this deposit 

 any well-defined fossils. Where the shale is replaced by indurated 

 clay in Tennessee, Dr. Troost says he has found Encrinites and Co- 

 rals, and also Orhulites lenticulata, Lam., and Favosites spongitesX, 

 The Encrinital limestone over the shale in Tennessee is rich in fos- 

 sils, often a mass of agglutinated Crinoidea. Troost enumerates 

 fifteen distinct species. Associated with these are Spirifer cuspi- 

 datus (?), S. attenuatus, and several species of Gorgonia, Flustra 

 and Turhinolia. 



The most characteristic fossils of the water-limestone are Atrypa 

 prisca^ Orthis lunata vel orbicularis^ LeptcBna lata (?), Terehra si- 

 nuosa, Tentaculites (new species?), Avicula reticulata (?), Calymene 

 bufoy Asaphus micrurus, and several other species undetermined ; 



* See Report of Ohio Geologists for 1838, p. 105. 

 + See Troost's Fifth Annual Report, pp. 16 and 17. 

 X Ibid. p. 17. 



