UPPER PALEOZOIC (dEVONIC). 241 
In the interior, where there was evidently a marine basin con- 
tinuously from the lower Silurian to the Carboniferous period, the 
Niagara, Hamilton and Sub-carboniferous faunas are scarcely 
more strongly contrasted than the three faunas of the members 
of the Cambrian system, and had we not such sections as are 
found in the east, or the precedents of European writers, it is 
doubtful if any good geologist would have distributed the rocks 
(for instance, those of Iowa between the Maquoketa shales and 
the coal measures) into three distinct geological systems of the 
Paleozoic. 
This great difference in the details of the passage from Devo- 
nian to Carboniferous in the several sections does not imply that 
one section is complete, and that where faunas are wanting there 
was of necessity a gap in the deposition, but rather that the con- 
ditions favoring the life of the fauna were wanting in the area 
where it fails. If our knowledge were complete, it is not likely 
that any strong separation lines would be recognized between 
faunas that are alike in widely separated areas. 
When we attempt to define the upper limits of the Devonian 
in terms of marine invertebrate fossils, it can be said that the 
line is indistinct and the evidence unsatisfactory in the eastern 
border region. In New York the highest invertebrate marine 
fauna is that of the Chemung stage. The Catskill stage in 
eastern New York follows the Chemung fauna in general, but 
the fact that species of fish and plants which characterize the 
typical Catskill rocks have been found in strata having Chemung 
fossils above them, makes it impossible to locate the precise 
equivalency of rocks marked only by the one or the other of 
these types of fossils. In Western Pennsylvania the Pocono 
series, including the Oil Lake stage, the Meadville stage and 
the Shenango stage of the 2d Pennsylvania Survey nomencla- 
ture, as applied by I. C. White (see Report Q. 4), follows the 
termination of the Chemung fauna, and contains the Waverly 
fauna of Ohio. In this region there is no true Catskill, but red 
shales, sandstones and conglomerates follow the zone bearing the 
Waverly fauna. Hence it is reasonable to conclude that the 
Pocono and Mauch Chunk of Pennsylvania, as well as the Cats- 
kill, the three together reaching a maximum thickness of no less 
than 10,000 feet, represent an interval in Western New York, 
between the termination of the Chemung fauna and the base of 
H 
