* 
428 J. J. Stevenson—Upper Devonian Rocks of Pennsylvania. 
and Conemaugh through Laurel and Chestnut Ridges, it will 
be seen that, as far as lithological characters are concerned, 
those rocks may be either Catskill or Chemung, though indeed 
the evidence seems to be rather in favor of their being Che- 
mung, for if one wished to describe them briefly and compre- 
hensively, he could do no better than to combine Professor 
Rogers’ descriptions of the Portage and Chemung, thus :— 
“A rather fine-grained gray and brown sandstone in thin 
layers parted by alternating bands of gray, blue, olive and red 
shales. It abounds in marine vegetation, and in the upper part 
the shales contain many fossils.” 
Since it would be excessively difficult to determine the rela- 
tions of these rocks by mere stratigraphy, and since the litho- 
logical characters fail to throw any distinct light upon the 
matter, the third test must be employed. 
What are the fossils? 
In the Summer of 1877, while making examinations in the 
Conemaugh Gap through Chestnut Ridge, I found, almost mid- 
way in the section given on another page, numerous specimens 
of Spirifer Verneuilir, Rhynchonella Stephani and Streptorhynchus 
Chemungensis, associated with many lamellibranchs and poorly 
preserved brachiopods, which could not be determined at the 
time. Further examination showed that these species occur up 
to within — inches of the undoubted Pocono sandstone, or 
The 
In order that no doubt might remain respecting these species, 
I sent some specimens to Professor Hall, who has made out the 
Langula, sp. ; 2. Discina grandis or D. Alleghaniensis ; 3. 
Streptorhynchus Chemungensis; 4. Rhynchonella Stephani ; 5. 
pirifera. Verneuilii; 6. Paicwoneilo maxima ; 7. Sanguinolites 
rigida ; 8. S. clavulus; 9. S. ventricosa? 10. Mytilarca Che- 
mungensis ; 11. Pteronites, sp.;.12. Pteronites, sp. ; 13. Actino- 
a recta ; 14. New form, undt.; 15. Orthoceras crotalum 2. 
These were collected at one locality and in haste, the only 
object aig Ba obtain a few specimens of the more common 
forms. Of the list, Nos. 6 and 18 are found in New York only 
in the Hamilton rocks, while No. 15 is ve closely allied to a 
Hamilton species and may be identical wit it; but reaping, 
the other forms there is no doubt—they are Chemung... Allo 
these forms occur also in the layers interstratified with those 
containing the fucoids, They are not stray specimens, such as 
might have been washed from the older into the newer rocks, 
