Chemung and Catshill.— Stevenson. y 
One Observer coming from the northeast along the easterly out- 
crop of the Devonian finds good reason to mark Catskill as be- 
ginning with the first appearance of red shales, while another 
coming from the west and south thinks that Chemung should 
close only with the final disappearance of the marine fauna. When 
these observers joined their work, their sections were in practical 
agreement, but were labeled very differently. 
The uncertainty respecting the relations of Chemung and 
Catskill is due in no small degree to the fact that the earlier 
studies of those groups were made in New York and adjacent 
portions of Pennsylvania, without much knowledge of the con- 
ditions elsewhere. Had the study been begun at the south in 
Virginia, then carried northward along the easterly outcrop 
through Virginia, Maryland and Pennsylvania into New York; 
then begun again in western New York or Pennsylvania and 
carried eastward to the outcrop, many difficulties, now apparently 
so formidable, would have been unknown and the problem of re- 
lations, seemingly so perplexing, might have been easy of solu- 
tion. At this time, however, the study can be prosecuted to 
better advantage than was possible even ten years ago, for the 
oil-borings of western Pennsylvania enable one to trace the beds 
through that region also, where in some localities they are more 
than 2,000 feet below the surface. Let us follow, then, the 
courses indicated, depending on the work of I. C. White, J. H. 
Carll and C. A. Ashburner in Pennsylvania, and that of J. J. 
Stevenson in Virginia and Pennsylvania, with references to the 
work of James Hall and H. 8. Williams in New York. 
i 
In the southwestern portion of Virginia, near the Tennessee 
line, the Devonian is represented only by black shale,* belonging 
at the base of the Hamilton; but within a few miles the Hamilton 
shows a greatly increased thickness,+ while between it and the 
Lower Carboniferous there are 350 feet of rock carrying Chemung 
fossils to within fifty feet of the top. The fossils are most 
abundant in a red or bluish rock with conchoidal fracture, which is 
the same in all respects, physically, with some non-fossiliferous 
*Stevenson, Proc. Amer. Phil. Soc. vol. XIX, pp. 223, 233, 243. 
Stevenson, Proc. Amer. Phil. Soc. vol. XXII, p. 136. 
