316 GEORGE H. GIRTY 
Another fact which might be brought forward to support the con 
tention that even the Hueconian is younger than the Kansas Permian 
is the important unconformity which preceded Hueco sedimentation 
and was accompanied by a corresponding change in the subsequent 
fauna. According to this interpretation, the oldest of the western 
faunas, which, as already noted, presents a closer resemblance to 
the characteristic Pennsylvanian fauna than any other, would corre- 
late with all of the eastern section to the top of the Kansas Permian. 
Its failure in the strata which it occupies to measure up to the thick- 
ness of the Mississippi Valley section, and the absence from it of some 
of the modifications found there, would be ascribed to pre-Hueconian 
erosion. After this episode there was, it might be claimed, a faunal 
change represented in the Hueconian fauna of the West and in Mr. 
Beede’s red beds fauna of Oklahoma, this in turn being succeeded by 
the Guadalupian fauna. 
Though keeping this interpretation of the facts well in mind, I am 
at present adopting the more conservative hypothesis—that the top of 
the Kansas Permian may be as high as the base of the Guadalupian; 
but that no part of the latter correlates with any part of the inverte- 
brate-bearing beds of Kansas.t From this it would follow that if the 
Guadalupian is equivalent to the Russian Permian then the Kansas 
Permian is distinctly older, possibly Artinskian, possibly Gschelian. 
If, on the other hand, the Kansas Permian is really equivalent to that 
of Russia, the Guadalupian would appear to be a distinct and 
faunally well characterized series younger than the Permian. 
It is well in considering the use of the word Permian for North 
American strata to discriminate Permian time, Permian conditions, 
and Permian faunas. Permian conditions, or conditions such as were 
prevalent in Russia during Permian time, might recur more than once. 
Indeed, it is safe to say that most conditions are repeated in one area 
or another many times during geologic history. Permian conditions 
would give character to the sediments and to the faunas. of Permian 
time. But, while the same peculiarities of sedimentation would 
presumably be manifested at every recurrence of Permian conditions, 
the character of the fauna would be partially determined by another 
factor, the biologic factor. It is conceivable, or evén probable, that 
t By this expression I mean to include the Marion and subjacent formations. 
