THE 
Peon NAL OF GEOLOGY 
OCROBER IN OVEMBE he. T0009 
BrvSiGAl GEOGRAPHY OF DHE PLEISTOCENE WITH 
SPECIAL REFERENCE TO PLEISTOCENE 
CONDITIONS 
ROLLIN D. SALISBURY 
The University of Chicago 
ae 
The character of the changes which marked the transition from the 
Tertiary to the Quaternary were somewhat unusual, though not 
unique as they were once believed to be. Great as these changes 
were, they were probably not equal in magnitude or importance to 
the changes which marked the transition from one great era of the 
earth’s history to another. ‘The significant changes at the close of 
the Tertiary are those which had to do (1) with the height and extent 
of the land and, perhaps as a result of these changes, (2) with pro- 
found alterations of climate, bringing on (3) glaciation on an extensive 
scale, and causing (4) migrations and mutations of life. 
I. THE PHYSIOGRAPHIC CHANGES 
The changes in altitude which affected the North American con- 
tinent late in the Tertiary have not, in most places, been worked out 
in such detail as to lead to numerical results in which implicit con- 
fidence can be placed; but the general tenor of the evidence is har- 
monious, and the main conclusions are probably correct in their 
general terms. They may be summarized briefly as follows: 
t Professor H. F. Osborn’s article on “‘ Environment and Relations of the Tertiary 
Mammalia,” No. XIII of this series, will appear in a later number of the Journal. 
Vol. XVII, No. 7 589 
