NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 85 



lines of many railroads at Pittsburgh, has been named from that locality. Occa- 

 sionally there is some limy gray or red shale under the overlying coal or limestone, 

 as the case may be, and then comes another limestone bed quite different in color 

 and texture, and only slightly fossiliferous. The limestone is found occasionally in 

 Ohio, and has there been named the Ewing limestone by the Ohio geologists. It 

 has been seen at Huntington and a few other localities in West Virginia, but does 

 not appear to be very persistent. As a rule, the measures below the Ames limestone 

 and Friendsville coal consist of deep red and variegated shales, often marly and 

 containing nuggets of impure limestone and iron ore. The red beds extend from the 

 Ames limestone downward from 50 to 100 feet. Although red sediments may occur 

 at any horizon in the Conemaugh series, between the Mahoning sandstone and the 

 Pittsburgh coal, yet these near the middle of the series are the thickest, most per- 

 sistent and striking of all. It is this band of Pittsburgh red shale, 30 to 100 feet 

 thick, which makes such a conspicuous belt of red soil entirely across the State, 

 from the Pennsylvanian line at the north to the Kentucky border on the Big Sandy 

 River." 



It is interesting to note that above the Conemaugh in the Monongahela 

 there is a change from limestone to red shale almost identical in character 

 with that which occurs in the Texas and Oklahoma regions. 



MONONGAHELA BEDS. 



In the north half of the State the Monongahela is nearly half limestone, 

 and no red shales. 



"In passing southwest from Harrison, Taylor, and Lewis Counties, however,* 

 the limestones practically disappear, along with most of the coal beds, while red 

 shales come in as the limestones go out, apparently replacing the latter, and the 

 sandstones grow more massive than in the northern area, thus giving origin to a 

 rugged topography and less fertile soils. 



"These rocks extend over a wide area along the Ohio River and for many miles 

 south of it, as far as the Great Kanawha, and in a narrow belt from that point to 

 the Big Sandy, where, in the center of the Appalachian trough, the lowest of these 

 beds passes into the air before reaching the Kentucky line. 



"No marine fossils have ever been discovered in any of the limestones of the 

 Monongahela series, and everything indicates that the deposits are of fresh-water 

 origin. The black slates always contain fish remains in the shape of scales and teeth, 

 but nothing is known of their affinities, because they have never been studied. The 

 water may have been estuarine and slightly brackish, but the minute Cyprian and 

 Estherian-like forms whose skeletons, mostly broken and pulverized, make up the 

 principal mass of the Monongahela series, testify clearly against their marine origin." 



With regard to the significance of the Pittsburgh red shale and its verte- 

 brate fossils, it is well to quote Dr. I. C. White,^ who remarks: 



"Viewed from the standpoint of change in physical conditions the proper place 

 for such dividing plane between the Conemaugh and Allegheny beds would be the 

 first general appearance of red rocks, near the horizon of the Bakerstown coal, about 

 100 feet under the Ames or crinoidal limestone horizon. That a great physical 

 change took place soon after the deposition of the Mahoning sandstone rocks, the 



» White, West Virginia Geol. Surv., vol. ii, pp. 124, 125, 1903. 

 b White, West Virginia Geol. Surv., vol. 11, p. 226, 1903. 



