The Pittsburg Coal Bed.— White. 5 1 
Waynesburg and Pittsburg coals, and in fact none until we 
pass below the Pittsburg seam several hundred feet, and reach 
marine conditions. The coal making epoch of the Appalach- 
ian Carboniferous really culminated and its decline began 
with the deposition of the Upper Freeport bed at the summit 
of the Allegheny River series of Rogers (No. XIII), since the 
few fossil plants found in the 600 feet of the Barren or Elk 
River strata which supervene between the PIpper Freeport 
and Pittsburg coals are either identical with or closely affil- 
iated to Coal Measure types of plants tliat survive into the 
Permian flora of Europe and Texas. This is also mainly true 
of the last marine faunal types occuring at the horizon of the 
Crinoidal limestone, about 300 feet below the Pittsburg bed, 
and therefore in Bulletin 65, U. S. G. Survey, page 19, the 
dividing line between the Lipper and Middle Carboniferous 
was drawn through the midst of the Barren Measures (No. 
XIV), at the close of the Crinoidal limestone stage when 
marine life became practically extinct in the Appalachian sed- 
iments. Hence the 6oo to 700 feet of strata extending from 
the Crinoidal limestone to the Waynesburg coal, and enclosing 
the great Pittsburg bed near the centre, may be considered 
as of Permo-Carboniferous age, or so far as there is any evi- 
dence to the contrary, they could just as well be classed as 
Permian. 
The flora of this portion of the column has been studied to 
only a limited extent, but so far as known, it consists as al- 
ready stated mainly of those Coal Measure types which pass 
on up into the undoubted Permian, while the faima com- 
prises only fresh or brackish water forms, concerning which 
little or nothing is known, as the fossils (mostly minute) have 
never been studied. The rocks themselves consist of a mon- 
otonous succession of red shales, gray sandstones, and lime- 
stones, often highly magnesian but only slightly gypsiferous, 
and presenting much the same lithological appearance from 
the Crinoidal limestone to the top of the Permian. 1,500 feet 
above the Pittsburg coal. 
The Neuropteris /iiorii Lx., and the large reptilian tracks 
found by Lyell near Greensburg, Pennsylvania, point to the 
same conclusion with reference to the age of the Pittsburg 
bed, namely that it. belongs to the closing stage of the Car- 
boniferous period, rather than to the middle of the same. 
