424 J. J. Stevenson— Upper Devonian Rocks of Pennsylvania. 
Lithologically, the top portion, No. 1 of the section, is a 
transition mass, more closely related to the overlying than to 
the underlying rocks. But its relations are clearly shown by 
the fossils which occur in it. This part of the section is well 
exposed in the several gaps referred to,-as well as on the 
National Road as it winds up the western side of Chestnut 
Ridge in Fayette County. At all localities examined it shows 
the same character, the sandstones are light-gray to brown and 
in thin beds, while the shales vary from brown to dull blue. 
but in both gaps of the Youghiogheny there are compact gray 
sandstones, good enough to be used for building purposes. On 
the National Road, ten or twelve miles south from the Youghio- 
gheny River, the shale and micaceous sandstones re-appear as 
on the Conemaugh. These micaceous sandstones are reddish- 
arder layers have their upper surfaces covered by a close mat 
of fucoids. : 
A curious conglomerate, from ten to twenty feet thick, 
sistent, having been seen under Chestnut Ridge on the Cone- 
maugh and Youghiogheny rivers as well as on the National 
are much larger than those seen in any other conglomerate 
exposed within southwest Pennsylvania. They are oval, thor- 
oughly rounded and polished as by long rolling in water. 
Most of the larger pebbles are quartz, but with them are others 
of felsite-porphyry, quite soft, which had been blackened exte- 
riorly before they were embedded in the material cementing 
mass, 
Relations of these Rocks. 
In the final report of the First Geological Survey of Penn- 
sylvania, Formation IX, the red Catskill of New York, is 
mentioned as occurring in the district under consideration. 
Following that report, I intimated in my second annual report 
to Professor Lesley that the rocks described in this article 
might be referred to that formation; on the maps accompany- 
ing my third annual report, now assing through the press, the 
areas are colored as Catskill. This which was done to pre- 
