A CIRCUM-INSULAR PALHA(OZOIC FAUNA, Q07 
study of this fauna Professor Williams* has shown that it was 
not the genetic successor of the fauna immediately preceding it, 
but that it was entirely foreign to the area, and that its relation- 
ships were with the Devonian faunas of western and northwest- 
ern America, which in turn were intimately related to the Euro- 
pean middle Devonian faunas. 
This earliest submergence of the Ozark Isthmus was not per- 
manent. The two seas were not in communication for a sufficient 
period to admit of any extensive intermigration of the faunas. 
A colony from the west escaped into the east and found its way 
into the New York region, where it occurs in the Tully lime- 
stone. From the oscillatory natures of the movements of this 
region during its period of submergence, there is reason to expect 
that there will be found in the Devonian beds along the border 
line between the eastern and western provinces a mingling of 
the two faunas. This need not necessarily occur in the same 
beds at first; the faunas might appear in alternate layers. Much 
yet remains to be done, however, upon the details of the strati- 
graphy and paleontology of this region. None of the present 
records enter into sufficient detail to be available for a conclusive 
study of the subject. 
On the final submergence of the connecting tracts and the 
formation of the Ozark Island—having approximately the area of 
the present exposure of the older rotks —the faunas of the two 
provinces had an unlimited opportunity to intermingle. It is this 
circum-insular fauna, found embedded in the strata of the Chou- 
teau group,’ which is the subject of chief consideration in this paper. 
The study of island faunas has always possessed the greatest 
interest to evolutionists. In his observations upon island faunas 
during his trip around the world, Darwin found many of the facts 
which led to his proposal of the theory of natural selection. 
* Bull. Geol. Soc. Am., Vol. I, pp. 481-500 (1890). 
?’The author may be criticised by some for using the name Chouteau, for these 
beds have of late come to be generally considered as contemporaneous with the 
Kinderhook, and designated by that name, which was applied at an earlier date. 
There is no doubt in the author’s mind of the contemporaneity of the Kinderhook and 
Chouteau, but the latter term is used as a convenient discriminative formation name ofa 
local nature to designate the beds deposited on the immediate shores of the Ozark 
