728 J. W. BEEDE 
those of the underlying horizons. The reason is that the faunules 
have not been quite so fully worked out and tabulated. However, 
they have been gone over in a preliminary manner and found to 
contain nothing, so far as I have observed, that is contradictory 
to the evidence presented. 
From the foregoing discussion of the Kansas faunas and the 
comparison of the elements in common (for it is largely upon the ele- 
ments in common that intercontinental correlations must be based) 
with those of Russia, there seems little reason for considering the 
Kansas faunas of Series III older than the Schwagerina-Cora horizons 
of Russia. Indeed the evidence is quite as strong in the opposite 
direction. 
GENERAL SUMMARY AND CONCLUSIONS ba] 
From what has been said it is apparent that during the Carbon- 
iferous period on the continents of Europe and America there was a 
long period of time during which favorable conditions obtained 
and the fauna was relatively varied, but, as many of the genera and 
species became paracmic, they were, in varying degrees, unable to 
adjust themselves to the changing conditions introduced more or 
less gradually with the Permian, and perished. ‘Those capable of 
least resistance perished first, and in the basal Permian we have a 
fauna made up of two elements in response to the physical and 
biologic conditions. First, the hardier forms which had passed their 
culumation and were on their decline. This is especially true of 
the brachiopods. They disappeared, not more, perhaps, from want 
of favorable conditions than from loss of vitality. Second, the 
pelecypods differentiated—possibly receiving recruits from other 
regions—and became the characteristic forms of the Permian. 
The one part of the Pennsylvanian fauna “grew old and died”’ 
assisted by changing conditions, while that part which had not pre- 
viously reached the acme of its existence differentiated into a fauna 
capable of inhabiting the more and more concentrated waters of the 
Permian seas. These classes of organisms being similar on the two 
continents produced similar results, whether or not the species were 
-identical. 
We may now summarize the bearing of the evidence of the stratig- 
