Chemung and Catskill,—Stevenson. 21 
Pocono. 573! 
Red shales, green and gray sandstones and concealed 830’ 
Fish conglomerate (Holoptychius bed) 2! 
Red shale and sandstone 200' 
The thickness of the rocks in the vicinity of Blossburg had 
been much underestimated by other observers. All the beds of 
the section below the Pocono haye been regarded by authors as 
Catskill, but at ten miles further down the Tioga river, three 
miles below Mansfield, Chemung fossils have been found by Mr. 
Sherwood in a calcareous rock,* only 165 feet below the bed 
taken as the base of the Pocono in Prof. White’s section, and 
therefore at more than 950 feet above the lowest red beds in that 
section. At a little way further east, Mr. Sherwood found great 
abundance of fish remains with shells and fragments of plants in 
the Holoptychius bed; a calcareous bed at 84 feet lower down con- 
tains abundance of well-known Chemung forms, while red beds 
continue in alternation with gray beds for 150 feet lower down in 
the column. In 1839, Prof. Hall connected his New York work 
with Pennsylvania at Tioga, eight miles further down the river, 
where he found the upper member of the Chemung passing under 
the Old Red sandstone, whose thickness he estimated at 400 feet. 
It is sufficiently clear that the red beds, including the fish bed, 
were regarded by him as belonging to the ‘‘Old Red Sandstone.” 
The McKean county section can be recognized without difficulty 
in Tioga county, despite the change in character of the rocks; for 
the middle division of Mr. Ashburner’s Upper Chemung finds its 
equivalent in ‘‘Mansfield Reds’ of Lesley, containing three ore 
beds near Mansfield, the second of which is the celebrated Holop- 
tychius bed. The base of the Red and Gray group in McKean is 
at 900 feet below the Pocono, while in Tioga county the Holop- 
tychius bed is at 830 feet. At the same time, the structure so 
well worked out by Prof. White in Susquehanna county, can be 
recognized with less difficulty than that of McKean. Eastward 
from the Tioga river, fossils become rarer in the upper part of 
the section; Mr. Sherwood states that no fossils occur in the 
Towanda basin of Bradford county until a bed is reached at 800 
feet below the Pocono. + 
Prof. White’s work in Susquehanna and Wayne counties, was 
connected by him with that in Bradford, which lies between Tioga 
*A, Sherwood, loc. cit. p. 79. 
tLoe. cit. p. 28. 
