20 The American Geologist. January, 1892 
the Catskill consisting of ‘red and grey slate, shale and sand- 
stone’ at Smethport, thirty miles east from Great Bend, in War- 
ren county. ‘The Chemung is triple, and its upper division is 
itself distinctly triple, consisting of 
Gray shale and sandstone 390’ 
Red and gray shale and sandstone 300' 
Gray shale and sandstone 650! 
the lowest beds resting on the Bradford oil-sand, which is Mr. 
Ashburner’s Middle Chemung. Typical Chemung mollusks oc- 
cur in the highest beds of the Chemung and some species appear 
to have persisted into the lower portion of the beds assigned to 
the Pocono. This abrupt thickening of Chemung and Catskill is 
precisely what should be expected here to accord with the condi- 
tions along the southern border of the state. 
The sections in Potter county, that adjoining McKean at the 
east, are incomplete, and our knowledge of the structure is far 
from being satisfactory. Mr. Ashburner made some examina- 
tions in the western part of the county, which were merely inci- 
dental and sufficed only to show that the ‘‘Catskill type” of rock 
increases in thickness eastward just as it does toward the south- 
east, there being 370 feet of red, gray and green shales and 
sandstones overlying the uppermost subdivision of his McKean 
county Chemung. He finds some red in his Chemung* as well as. 
in the overlying Pocono. Fish beds occur in his Catskill as well 
as in the upper part of his Chemung. No information is given 
respecting distribution of molluscan remains, but on the eastern 
side of Potter, Chemung forms extend far up into the red beds, 
for, just over the border in Tioga county, Chemung fossils are 
found at more than 300’ above the first red beds. t 
The condition in Tioga and Bradford counties, those next at 
the east, is sufficiently clear. Prof. White’s incidental studies in 
those counties make it possible to utilize Mr. Sherwood’s work, 
and at the same time to gain a good understanding of the work 
done by Prof. Hall and Mr. Vanuxem more than fifty years ago. 
The section near Blossburg, in Tioga county, gives a starting 
point.{ It is 
*Loe. cit. pp. 77-78. 
tA. Sherwood in Report of Progress in Bradford and Tioga counties. 
Harrisburg, 1878, p. 86. 
tGeology of Susquehanna and Wayne Counties. I. C. White, 1881, 
p. 72. 
