Siijjerior JIi.ss/t<!iippi(i/t in Jlissonri <i)td ^[ rkc jisas. — A'ej/es. 87 
In geographical extent the ro?ks of the Mississippian series 
present some striking peculiarities which have an important 
bearing upon the question of the range and character of the 
contained faunas. Beginning in north-central Iowa near the 
Minnesota line, where the Carboniferous passes beneath the 
Cretaceous, the Mississippian rocks extend southeastward in 
a broad belt to the river from which the formation takes its 
name. From southern Iowa the Lower Carboniferous lime- 
stones continue southward along the great stream on the east- 
ern border of the Ozark iiplift and sweep through Kentucky 
and Tennessee into Alabama. In northeastern Missouri 
another zone stretches around the northern and western flanks 
of the uplift through southwestern Missouri, northwestern 
Arkansas and Indian Territory, extending, discontinuously 
probably, as far as New Mexico. 
The Lower Carboniferous rocks which are exposed along 
the Mississippi river were carefully studied and the fossils 
and succession of beds clearly made out long before any other 
portion of the area had been satisfactorily determined. It 
was on this account and for the reason that the rocks of this 
age are so excellently and fully exposed on the stream that it 
became eminently proper to designate the strata as the Mis- 
sissippian series. The section disclosed thus becomes the 
principal one and the standard of comparison. To it sections 
of different localities in the interior basin must be referred 
and with it all correlations made. 
A review of the geological work done previous to 181)1 in 
•southwestern Missouri and the adjacent territory shows clearly 
that not only difficulties of interpretation were encountered 
but that no serious attempts were made to compare the suc- 
cession with those of other localities. The want of details and 
the uncertainty which surrounded the various accounts of the 
region have been in great measure relieved by recent ])ersonal 
visits to some of the more important localities. The inferior 
portion of the Lower Carbonil'erous was found to be as fully 
■developed and as clearly defined as in the typical localities in 
southeastern Iowa. The superior ])ortion of the series — that 
part comprising the St. Louis and Kaskaskia limestones — did 
not api)ear to be represented. Only a few of the localities ex- 
amined gave evidence of the higher faunas and none of these 
were conclusive enough t;) settle the ((ue.^tion satisfactorily. 
