502 E. C. CASE 
It is just this factor of climatic change that the author proposes 
to use in the interpretation of the change of environment in late 
Paleozoic and as a basis for the correlation of “‘ Permo-Carboniferous 
conditions”’ as opposed to a correlation of a certain group of beds 
within definite stratigraphic limits. ‘‘Permo-Carboniferous con- 
ditions,’ as here used, involves the idea of an interval of time, but 
not of the same duration in all areas where such conditions pre- 
vailed, for, as will be shown, the conditions were developed pro- 
gressively across a large area and the base of the deposits governed 
by such conditions cut obliquely across the stratigraphic column. 
In the case here discussed the shape of the deposits so governed is 
that of a flat wedge, for the conditions persisted where they were 
SS = === Dunkara 
=| Monongahela 
Conemaugh 
Fic. 1.—Diagrammatic illustration of the relation of ‘‘ Permo-Carboniferous 
conditions”’ to the late Paleozoic stratigraphy. No account is taken of the breaks or 
the present geological structures. The dashed area indicates ‘“ Permo-Carboniferous 
conditions.” 
first established and the progress of the conditions led to ever 
thinner deposits toward the outer limit (see Fig. 1). It is con- 
ceivable that under other circumstances a uniform set of conditions 
might pass across a large area as a wave, and the resultant deposits 
would then be detected in the stratigraphic column as a band of 
greater or less thickness oblique to the normal bedding-plane. 
As shown in the abbreviated correlation table below, the 
Dunkard with its typical Permo-Carboniferous flora, fauna of 
invertebrates, and single characteristic vertebrate (Edapho- 
saurus) is by all commonly accepted canons of correlation and 
by its stratigraphic position the very approximate equivalent of 
the Wichita-Clear Fork beds of Texas, but both red beds and 
Permo-Carboniferous vertebrates are found far below this horizon 
in both Pennsylvania and West Virginia. In Pennsylvania, 
Raymond found vertebrates closely similar to those occurring in 
Texas in the Pittsburg Red Shale, 500 feet below the top of the 
