346 Tlie Amertca7i Geologist June, isoo 
represents a commingling of forms which characterize two or 
more distinct periods in another part of the country. Such 
cases as the latter we have in the Anticosti group, where Up- 
per and Lower Silurian species are mingled together in a ser- 
ies of rocks of great thickness and peculiar lithologic charac- 
ters ; and in the Cincinnati group where Lorraine, Utica and 
Trenton fossils are intermixed. 
But where a difference in lithologic characters alone exists 
without any marked change of fauna or of position in relation 
to other known groups ; or where a horizontal distance sepa- 
rated two eras which were once supposed, but at a later period 
are shown not to be separated by any great break in continui- 
ty ; then if a new name be given and a new division formed, it 
can not readily stand the test of investigation. Thus we 
believe the Maquoketa cannot retain its autonomy even as a 
formation distinct from the Cincinnati group for the following 
reasons : 
1. In position with relation to under and overlying rocks 
they are the same. 
2. In lithologic characters there is no difference that can be 
noted; both consist of calcareous shales and thin bedded lime- 
stones. 
3. In palaeontological features they are almost counter- 
parts, only a single species out of 41 being confined to the 
Iowa series ; and 
4. They are in actual fact, the extension of the Cincinnati 
group as exposed in southern Ohio. 
Of these four reasons we shall take up the last first. We are 
the better able to examine into this subject because of the ex- 
tensive search which has been carried on in Indiana for Nat- 
ural Gas. The underground geology, as professor Orton has 
termed it, has become an important adjunct to above ground 
geology. By means of the records of well borings we can trace 
the extension of series of rocks long after they have buried 
themselves beneath the surface. The Ohio Geological Survey 
has taken a leading part in placing upon record and discuss- 
ing the facts the wells have revealed, and Indiana has done 
something in this way. But we are especially indebted to the 
industry of Mr. Frank Leverett, who, while engaged in tracing 
the moraines of Indiana for the United States Geological Sur- 
vey, collected such well records as he could in the course of 
