82 CONTRIBUTIONS TO DEVONIAN PALEONTOLOGY. [bull. 244 
cases a is therefore misleading- on account of misinterpretation of the 
fossils. 
While this reliance upon wrong report of fossils has led to error 
a mistake of another kind was made when I. C. White held that 
Chemung species occurred not only in his transition interval, called! 
Chemung-Catskill, hut also several hundred feet ahove the base of the 
Catskill. b This is accounted for by the supposed survival of Chemung 
species into the Catskill age. u But the marked absence of other 
well-known Chemung fossils shows that the above-mentioned species 
are merely five species which survived long beyond those with which" 
they are associated in the genuine Chemung beds, into the Catskill 
age.' v> The same idea is conveyed in an earlier statement in which 
the author defends his determination of the base of the Catskill at the 
Holoptychhis beds by saying: "Some geologists would doubtless cut] 
off the Catskill at the base of No. 22, and place all of the underlying 
portion of the section, 700 feet thick, in the Chemung, because some: 
shells of Chemung type occur in these beds; but since more than 1,000 
feet of red beds underlie the fish bed, No. 54, at the bottom of the sec-] 
tion, I prefer the conclusion that a few of the Chemung shells lived on, 
in this region at least, far into the Catskill period." c I quote this argu- 
ment in full because it strikes at the very heart of the difficulty. 
The first appearance of red beds and of Jloloptychius in a strati- 
graphical section is there announced to be of more importance in deter-] 
mining the geological age of the beds than the presence of well-known; 
representatives of a marine invertebrate fauna which is known to hold 
a definite place in the sequence of fossil faunas. 
The problem may be expressed in simple terms, as follows: It is 
supposed that Spirifer disjunctus is characteristic of the Chemung 
fauna and red beds are typical of the Catskill formation. Where 
Spirifer disjunctus occurs in the midst of red beds I. C. White main- 
tained that the rocks are of Catskill age and that Spirifer disjunctui, 
lived on after its normal period (the Chemung). The opposite conten- 
tion, which is here advocated, is that the age of the beds is Chemung 
and that the red beds were deposited earlier in this region than at 
places where they are found only above the Spirifer disjunctus zone* 
of the section. 
The issue was clearly recognized by me at the first reading of 
Report G 7, but it will be noticed at once that the question seems to 
be purely a matter of opinion, and there is no evidence to prove the 
correctness of either view. At the time of writing the report its 
author and the Pennsylvania survey were apparently in possession of 
the facts. The disregard of the interpretations by fossils was justi- 
fied, since the species were incorrectly reported in a critical case. The 
problem could be solved only by such a perfect elaboration of the 
aSee Second Pennsylvania Geo]. Survey, Rept. G 7, PI. V., p. 66. t> Ibid, p. 240. clbid, p. 59. 
