286 REVIEWS 
in the final chapter, of the evolution of man himself. Nor does this brief 
summary of the contents of the volume include instructive chapters on 
the physical basis of life, classification of organisms, the geological, 
geographical, and bathymetrical distribution of organisms, and on the 
extinct dinosaurs in particular. 
Few available sources of information have been overlooked, and in 
an attentive reading of the book the reviewer has found very few mis- 
statements of facts. Various disputed theories of the origin of organisms 
or their functions are discussed, but the author, commendably, has not 
ventured many himself. 
In a few words the work is an excellent summary of the theories, 
facts, and factors of evolution, adapted especially to the needs of the 
student and presented in a readable way. The sao as well as the 
biologist will find it of interest. 
S. W. W. 
Geology and Geography of the Galena and Elizabeth Quadrangles. 
By A. C. TROWBRIDGE and E. W. SHAw, with chapter on the 
“History of Development of Jo Daviess County,’’ by B. H. 
SCHOCKEL. Illinois State Geol. Survey, Bull. 26, 1916. Pp. 
DRE 1NSy BS. ines, Ife), 
The district lies in the extreme northwest corner of Illinois, almost 
entirely within the Driftless Area. The lead and zinc deposits having 
been described in previous reports, the present writers discuss the 
general geology of the region and the processes which have produced 
its topographic features. 
The Platteville limestone, Galena dolomite, Maquoketa shale, and 
Niagara limestone outcrop within the quadrangles; deep wells have 
penetrated the Potsdam, Prairie du Chien (=Lower Magnesian) and 
St. Peter formations. The Quaternary deposits include fluvio-glacial 
terrace materials, more or less isolated areas of loess, a small area of 
Illinoian (?) drift, and recent valley alluvium. 
The work of wind, ground water, and stream erosion are discussed 
at length. The origin of two surface levels above the present valleys 
is considered, and though the evidence collected here is nof decisive 
proof of peneplain origin, data from adjoining districts warrants the 
acceptance of that hypothesis. The age of these surfaces is uncertain. 
Following Salisbury, the writers suggest that the Niagara flat is of 
Pliocene age and the Galena flat earliest Pleistocene. 
