“ 
26 The American Geologist. - January, 1892 
in general conditions were insignificant from the beginning of the 
Portage to the close of the Chemung; at all events the changes 
in by far the greater part of the area under consideration, were 
not such as to interfere materially with the existence of the 
molluscan fauna known as Chemung, though as we have seen, 
there were circumscribed areas in which the conditions did prove 
very injurious to animal life. 
The Chemung and Catskill are very distinct, paleeontologically, 
along the eastern outcrop in southern Pennsylvania. The Cats- 
kill, almost wholly red shale and red or greenish-gray sandstones, 
appears to be non-fossiliferous; but the Chemung carries its fos- 
sils to practically the top of the Montrose shales. The condition 
is unquestionably the same in northern Virginia. Near the Ten- 
nessee border, the equivalent of the Montrose sandstone has 
Chemung fossils; at New River gap, Chemung fossils were not 
found in the upper half of the interval between the Lackawaxen 
and the Pocono; in MecAfee’s gap in Roanoke county, proof is 
shown that Spirifera disjuncta survived all changes to the end 
of the Catskill; while at eight or ten miles southeast in Catawba 
mountain, the whole succession of red greenish-gray sandstones 
seems to be absolutely non-fossiliferous; and this is the prevailing 
condition thence northward. It is evident, then, that from, say, 
twenty-five miles southwest of James river in Virginia to New 
York, the group called Catskill by Vanuxem is either non-fos- 
siliferous or practically so. But the Chemung group contains its 
characteristic species above the Lackawaxen conglomerate in Vir- 
ginia and along the eastern outcrop into Montour county of Penn- 
sylvania; so also in southern Pennsylvania* westward to where it 
passes beneath the surface beyond the final disappearance of 
Catskill in Fayette and Westmoreland counties; while in north- 
western Pennsylvania and along the northern line of the state, 
Chemung forms are present in the same upper horizon from the 
Ohio line eastward into Bradford county. In New York on the 
northwest border of the Catskills themselves, Chemung fossils 
occur abundantly above the Oneonta? sandstone which Vanuxem 
identified with the Montrose sandstone of Pennsylvania. 
*In my report on the Geology of Bedford and Fulton counties, p. 81, 
I identified the conglomerate of the Laurel and Chestnut ridge gaps 
with the Lower (Allegrippus) conglomerate. The error was discovered 
too late for correction. 
+James Hallin Sczence 1880, p. 290. 
