The Missourian Series of the Carbo7iifcrous. — Keyes. 30 1 
Heretofore no attempt has been made to harmonize the 
numerous isolated exposures or to make complete the exact 
sequence of strata from the base to the top of the series. 
The earliest investigations in the region did not attempt to 
estimate the vertical extent of the various strata that compose 
the Missourian series. Those who entered the district under 
the auspices of the several states bordering the Missouri river 
all considered the beds, as a whole, very much too thin. Usual- 
ly these estimates were only one-fourth to one-sixth the real 
values, bringing the total down to 300 and even 200 feet. 
Nearly every one of these writers manifestly confused the dif- 
ferent limestones, not recognizing that there existed several 
very distinct formations very much alike in general charac- 
ters. This is notably the case with Swallow, Hawn, White, and 
their associates. Since Broadhead's work of 1872. there has 
been a general tendency to greatly over-value the real thick- 
ness of the series. Nearly every one of these later writers, who 
has given the matter consideration, placed the figures at five 
to ten times as great as the earlier calculations. Without ex- 
ception these estimates also have been based upon insufficient 
observations. They have in no case extended over the whole 
field. 
The Missourian Series. 
Relations to the Other Carboniferous Series. Since the 
Carboniferous rocks of the Mississippi valley first came into 
notice, over half a century ago, various classifications have 
been suggested. As recently stated little detailed investigation 
was done having for its special object an arrangement for the 
whole region. In consequence the subdivisions that were pro- 
posed, differed widely ill the different states and even in differ- 
ent parts of the same state. 
Of late, the lower Carboniferous in all its minor parts has 
been satisfactorily correlated over all of the northern Interior 
basin. The lower coal measures have also been subdivided in 
a way that enables the various members to be widely recogniz- 
ed. The so-called Permian has received attention. The major 
sub-divisions of the Carboniferous of the region are now pretty 
well defined. 
Distinguisliing Characters. In all of the six principal 
