244 Recent Literature. [ April, 
refer chiefly to the exposures which the author has visited along 
the line of the Union Pacific railroad, and but little information 
is furnished respecting the strata of the Laramie on the middle 
and upper Missouri and the Saskatchewan regions. Then follow 
the detailed descriptions of three hundred and twenty-nine species 
of plants, many of which are represented by numerous remains, 
and from various localities. This portion of the work is illus- 
trated by sixty-five plates, well executed by T. Sinclair & Son, of 
Philadelphia. Here the author supplies his fellow students with 
the most valuable evidence as to the characters presented by this 
vast department of life during the past periods of the existence of 
our continent. 
e work closes by a general discussion of the meaning of the 
evidence with regard to the mutual relations in time of the 
various formations treated of, and their correspondences to the 
horizons of other countries. He reaffirms the conclusions pre- 
viously stated, viz: that the flore from the base of the Laramie 
upwards is of tertiary age. He divides the series into four 
groups, all of which (p. 352) he regards as belonging to the 
“ Lignitic formation.” He thus parallelizes them with the Euro- 
pean standards (p. 354). “I admit the lower group as Lower 
Eocene; the second group, which seems intermediate between 
this and the Carbon, may be Upper Eocene; the relation of the 
third group is by its plants with Lower and Middle Miocene of 
Europe, and that of the fourth with the Upper [Miocene]. These 
are like the first outlines traced for the preparation of a map; 
they may be erased or modified, the spaces have to be filled as 
our acquaintance with the Tertiary becomes more intimate.” 
The evidence in favor of the correctness of these positions 1$ 
an 
d not be 
accepted by students in other departments. Nevertheless the 
value of the evidence derivable from these vegetable remains 1S 
only to be fully understood by comparison with that derived from 
all other sources, 
the evidence they offer as to the age of the horizons both in their 
mutual relations and their relations to the formations of 
countries, is quite different from that presented by Prof. Lesque!- 
e t is well known that I was the first to show that the ver 
tebrate fauna entombed in the lignitic formations to the mm 
of the Laramie, or to the summit of Prof. Lesquereux’s firs 
ee i ai PCE e a aa E eR ire E e o a e e a A S a O O pe Neer eee riie Bn es 
E E E A A E EEI ES E EA D L S A ea AES EET 
