988 The American Naturalist. [November, 
Correlation Papers issued by the U. S. Geological Survey. Originally 
Mr. Russell intended to cover the entire Jura-Trias of North America, 
but circumstances compelled him to restrict his attention to those of the 
Atlantic border. This particular body of rocks the author calls the 
Newark System, a name proposed by W. C. Redfield in 1856, giving 
as a reason that it is the oldest specific title not implying opinion as to 
geologic age. These rocks extend from North Carolina to New Bruns- 
wick and Nova Scotia, but not to Prince Edward’s Island, as has been 
asserted. They occur in narrow belts trending parallel to the appli- 
cation folds, covering an area of 10,000 square miles. It is Mr. J. 
Russell’s opinion that the evidence now at hand bears out the theory 
that these detached areas are remnants of a once broad terrace which 
has been broken by orographic movements and greatly eroded. 
The sedimentary rocks of the Newark System, consisting chiefly of 
sandstone and shale, were deposited in tide-swept estuaries, while the 
carbonaceous shales and coal seams originated in basins more shut off 
from the seas. The trap rocks are a part of the great system of dikes 
and sheets which intersect the surrounding crystalline and paleozoic 
rocks. The evidence of glacial action during the Newark period, Mr. 
Russell thinks is weak. 
In diseussing the relations of the Newark system to other terranes 
the author refers to the difficulty of correlating the rocks of America 
with those of other countries, and concludes that biological phenomena 
as a means of correlating, can be safely used only after the relative 
age of the strata has been determined from physical phenomena, 
Paleontologists of the Vertebrata will not concur in this view, for the 
vertebrate fossils indicate conclusively that the formation contains at 
least the representation of the upper member of the Trias or the 
Keuper. This was first definitely pointed out by E. D. Cope in 1866. 
The volume is accompanied by a very full bibliography, and is illus- 
trated by many handsomely executed colored and uncolored plates. 
The colors of the geological maps are in general accordance with those 
in use by geologists. 
Spalding’s Guide to the Study of Common Plants. It isa 
pleasant thing to take up a new book and find our expectations not dis- 
* Proceedings of The Philadelphia Academy, pp. 249-50, 290. This reference is 
omitted by Mr. Russell from his table of determinations on p. 17, but is included in’ 
the Bibliography on p. 170. 
5 An introduction to Botany. By Volney M. Spalding, Professor of Botany in the 
University of Michigan. Boston, U. S. A. D. C. Heath & Co., Publishers, 1893, pp. 
XIII 246. ; 
