OP THE 
UNIVERSITY of ILLINOIS. 
Dual Character of the Kinderhook Fauna. 175 
Third. One reaison that the fauna of the Chouteau (origi- 
nal) limestone has not been better understood in its relations 
to the faunas occurring lower in the so-called Kinderhook, 
and higher in the Burlington limestone, has been that in the 
localities where the lower Carboniferous has been most thor- 
oughly and widely studied, that is along the Mississippi river, 
the Chouteau, as commonly recognized nowhere crops out 
along the great stream, except perhaps in the vicinity of the 
town of Louisiana, where, under the typical Burlington, there 
is an earthy limestone six to twelve feet thick, which has 
been considered a part of the latter, but which is not believed 
to be the attenuated edge of the Chouteau or its equivalent. 
At any rate in the immediate vicinity the undoubted Chou- 
teau attains a thickness of fifteen to thirty feet. 
Over two hundred species of organic remains have been 
identified at Louisiana in the so-called Kinderhook and the 
Burlington beds. By arranging these according to the faunal 
zones recognized several important facts are brought out. It 
is found that at the base of the Chouteau limestone there is a 
line on either side of which there is, with one possible excep- 
tion, not a single species that is found on the other. Forty- 
three species occur in the "Kinderhook" below; 157 in the 
strata above. The one doubtful case is a possible variety of 
Spirifer hann/'balensis, a widely distributed type. Thus the 
upper fauna nowhere extends beneath the base of the Chou- 
teau ; and the lower fauna nowhere rises above the same level. 
The species belonging to the fauna beginning in the Chouteau 
extend upward into the Burlington. While in the latter manj'' 
new forms appear they do not immediately replace the typi- 
cal Chouteau types. The strangest feature of all is that the 
many new species which appear in the second bed of the Bur- 
lington, some ten feet above the base of that formation, are 
largely so-called Kinderhook forms, not altogether from the 
Chouteau of the immediate neighborhood but from the lime- 
stones which occur just beneath the Burlington limestone in 
other localities, as in the city of Burlington. 
The following general conclusions are deduced: 
1. The most marked change in the succession of faunas in 
the entire sequence of rocks commonly known as the lower 
Carboniferous or "Subearboniferous" as represented along 
