Recent Publications. 61 
anyextent. It having been demonstrated that classification cannot be 
based upon the uniformity of lithological constitution, and that uni-. 
formity of stratigraphy cannot be relied upon for correlations “the 
modern school of paleontologists are demonstrating the fact that the 
divisional lines marking the biologic or time scale do not correspond to 
those of the structural or stratigraphic scale, but are determined by in- 
dependent factors. In the classification of rock furmations the character 
of the formations should receive chief consideration, but the particular 
geologic period in which the sediments are deposited has practically no 
relation to the nature of the sediments or their amount or their physical 
arrangement as geologic deposits. It is, hence, a grave question 
whether the development of our science does not demand that geo- 
graphic factors should take precedence of time factors in all classi- 
fications of geologic formations.” (p. 267.) 
The standpoint of the new school of paleontologists of which professor 
Williams is an able exponent, is summed up in the concluding para- 
graph of the Bulletin. According to the Darwinian idea of species, as 
opposed to the Cuverian, “the modification of organic form is conceived 
as not an arbitrary matter, but as correlated with difference of envi- 
ronment and of genetic relationship, so that the lesser variations of 
specific form are of as great value to the modern paleontologist for pur- 
poses of correlation as is the identity of species. Comparison of allied 
species in the same genus exhibits to him the rate and direction of 
modification taking place in the genetic history of the genus, and in the 
plastic or variable characters he finds a sensitive indicator of the stage 
of development attained by the race when the particular individual lived. 
Biological study shows him that the fossils must contain intrinsic 
evidence of their geologic age independent of the formations in which 
they were buried,and his chief work is to learn what this evidence is and 
how to interpret it. To such evidence the final appeal must be made in 
all cases of the correlation of geologic formations.” (p 269.) 
Taken as a whole the Bulietin under review cannot but be regarded 
as a valuable contribution to the philosophy of geology; and while some 
of the conclusions of the author may not meet with the approval of 
all, they at least merit consideration. Some portions of the volume show 
signs of haste in preparation; and it would have been a valuable addi- 
tion had there been given a list of the books and papers consulted or re- 
ferred to in the course of preparation of the Bulletin. 
RECENT PUBLICATIONS. 
I. State and Government Reports. 
Annual Report of the Geological Survey of Arkansas, 1888. Vol. IV. 
Part I. Geology of Washington County; Part IT. List of the Plants of 
Arkansas. 
Ditto, 1890. Vol. I. Manganese: Its Uses, Ores, and Deposits. By 
R. A. F. Penrose, Jr. 
