328 University Geological Survey of Kansas. 
hand, the faunas occupying the epicontinental seas for great 
lengths of time were protected from both these influences, 
and as a consequence led a more peaceful and longer existence, 
permitting the study of their characters through a much 
greater length of time. The recognition of these principles, 
if they be correct, is of double significance in correlation. 
There is small difficulty in recognizing the relative stages 
in the life-history of a species, especially of brachiopods, to 
one familiar with them, and they are an indication of the time 
when the migration into a region took place if the specimens 
of a species are all from a single stage of the life-history. If 
these features are not recognizable there is then more or less 
probability that the migration took place during culmination. 
For example, Squamularia perplexa (McChes.) is so abun- 
dant in the Pawnee and Altamont limestones as, locally, to 
contribute very largely to the formation of the stone. Speci- 
mens of it are fairly abundant until the Oread limestone is 
passed, when it becomes rarer, and finally disappears in the 
Howard limestone. The earlier specimens are smaller than 
the later, which are large, thick-shelled, and show the char- 
acteristics of old age. It is believed that in such cases as this 
the species is much more likely to perform migrations in its 
earlier stages of existence than in its later stage, with its 
senile characters and rare occurrence. 
Faunal Distribution. 
Space will permit but a mere mention of the more striking 
features of the distribution of the species of the faunules of 
the various horizons, which are more complicated than one 
would expect. This distribution was probably profoundly 
influenced by the presence of a varying shore-line to both the 
southeast and east of much of this area, while to the south of 
the younger, or western part of the section, shallow water or 
occasional beach conditions occurred on the south in Okla- 
homa. 
These last conditions continued long into the Permian and 
produced a rather marked change in the fauna of the southern 
end of the upper horizons in tending to retain some of the 
shallow-water species after they had disappeared from 
the northern part of the region. The conditions affecting 
the northeastern and eastern faunas discussed below were 
probably those incident to the coast of any very shallow epi- 
