420 The American Naturalist. [May, 
the Ozark region. The former has an elevation ranging from 800 feet 
along the Mississippi to 1200 feet in the northwestern corner of the 
state. The Ozark region originates in a centre distinct from the Prairie 
district of elevation. It forms a large part of southern Missouri and 
portions of adjoining states with a maximum elevation within the former 
of 1700 feet. 
The upland plain is broken by a number of escarpments formed by 
outcropping edges of hard strata underlain by softer rock. A number 
of these escarpments are described and the more pronounced are shown 
on a sketch map. Between successive escarpments lie platforms or 
belts each with their peculiar, surface features depending on the char- 
acter of the underlying rocks. The report concludes with an excellent 
account of the development of the streams, the subject of river mean- 
derings receiving special attention. 
In the report on the formation of the Quaternary deposits the author 
gives the distribution and limits of the surface formations of Missouri. 
The general character and relations of the several classes are thoroughly 
described. The quaternary deposits of the state are divided into (1) 
the Bowlder Drift, (2) the Loess and Gray Loamy Clay, (3) Terrace 
_ Deposits, (4) Alluvium. The characteristics of each class are clearly 
set forth and their limits shown on a sketch map. As the drift does 
not extend, beyond the Missouri river the formations treated in the re- 
port lie almost wholly north of that stream. The report concludes with 
a summary of the quaternary history of Missouri. 
The Bibliography of Missouri Geology is very full and complete, the 
plan being that of a dictionary catalogue or bibliographic index. There 
are included an author’s list, a title index and subject entries and cross 
references. The advantage of this plan is that it is unnecessary to turn 
back from one title to another to obtain a full bibliographic reference. 
Volume XI, is devoted entirely to a report on the clays of Missouri 
by H. A. Wheeler. Such thorough and complete treatment of its clays 
has never been undertaken by any state. The physical and chemical 
properties of clays receive especially full treatment. Thus consider- 
able space is devoted to the subject of the plasticity, fusibility and 
shrinkage of clays, one chapter being devoted to each. A microscopi¢ 
study of the clays was also undertaken with interesting results. A sur- 
prising variety of deposits are found throughout the state. Each 
variety is treated separately and its physical and chemical properties, 
distribution and adaptability to particular uses described. A chapter 
that will prove of much practical value is the one devoted to the tests 
and analyses of clays. Not only are the analyses of Missouri samples 
