The Ci((le}i(( and Jlaquokefa Series. — S(irdeso)i. 357 
only the local names, the definition of wliich has been verified 
through type exposures existing within the area itself. 
As said, the Galena and Maquoketa series are not uniform- 
ly and consistently defined in each state, nor even Indifferent 
counties of the same state, but varying limits are assigned to 
them. Some time ago the writer tried to outline a more uni- 
form and more detailed classification of the Galena and Ma- 
quoketa series than before existed,* but the same work 
remains in part to be completed. After having made consid- 
erable further investigation it is now intended to advance 
again in the same direction, and since the publications that 
have in the meantime svirveyed the same ground more or less 
completely have by no means shortened the way, but on the 
contrary have placed the beginning a little back from the 
point before reached, we will act accordingl}'. 
In this discussion there will be considered, first of all, the 
classifications by authors generally, and tables of synonomy 
for each division and subdivision will be given, after which a 
better classification will be outlined. 
The Galena series and the Maquoketa series are very favor- 
able for exact division and delimitation and for correlation of 
one exposure with another, because the strata are relatively 
horizontal and quite undisturbed, because fossil remains are 
numerous, often well preserved and accessible, and because 
the division and subdivision are guided by many lithologic 
differences. The subdivisions are, moreover, nearly all co- 
extensive and often constant in original thickness. All taken 
together are not over 450 feet thick, and several beds may be 
found in single exposures. It is possible, therefore, as it is 
also necessary, to combine stratigraphic, paleontologic, and 
lithologic evidence to work out the relations to each other of 
the parts of these two series. The reason why greater uniform- 
ity in classification has not obtained is found apparently less 
in the nature of the formations than in the custom of limiting 
research to the bounds of states and counties. Both the series 
and their subdivisions being traceable continuously from Min- 
nesota through Iowa to Illinois and Wisconsin, one system of 
division and of nomenclarure would have been the inevitable 
result of wider investigation by each author. But, in the man- 
*Bull. Minn. Acad. Nat. Sci., vol. iii, p. 319 (1892). 
