SOUTH AMERICAN GEOLOGY 
215 
changes in level. This evidence receives full confirmation from 
Bowman’s physiographic studies in the Andes, and explains the 
distribution of the existing birds and fresh-water fishes, as set 
forth in such a masterly way by Chapman and by Eigenmann re¬ 
spectively. The post-Pliocene elevation with the consequent cli¬ 
matic changes west of the Front range is estimated by me at not 
less than 6500 feet and possibly as much as 9000 feet. 
This region commenced its elevation as a country of mature 
erosion and low relief. Concomitant with elevation and waste- 
slope deposition went intrenchment of the streams. The Rio la 
Paz, the only river which cuts the Cordillera Real, appears to date 
from this time or even earlier, trenching an area of soft Devonic 
shales lying in a saddle between the Illimani and Quimsa Cruz pro¬ 
jections of the Illimani batholith. With the attainment of maxi¬ 
mum elevations in the Pleistocene came glaciation, which shows 
two maxima. So far as I can discover the Andean glaciation was 
wholly of the Montane type, and did not reach low levels, except 
in the extreme southern part of the continent. In Bolivia and 
Peru the lower limit of this glaciation is about 2500 feet below the 
present lower limit, but the data are much masked by the prevail¬ 
ing aridity of the region at the present time. Thus, at Potosi, the 
Cerro has no permanent ice-cap, although it reaches an elevation 
of 15,500 feet, whereas the terminal moraine lies below the town 
at about 12,500 feet. 
In summing up the evidences of former land-connections, I 
omit all detailed consideration of Central American-Antillean land- 
connections, since so much has been written about them recently* 
The evidences for Antarctic association are: 
Slight importance is attachable to submarine topography, so far as it 
goes it is confirmatory. 
Common Mesozoic and Tertic land-plants are clearly derived from South 
America. 
Similarity of diastrophic history throughout Mesozoic and Cenozoic 
times. 
Identity of igneous rocks . 
Recent sinking of Coast Range and flooding of the longitudinal valley 
of southern Chile. 
Fossil Araucarian forests in the Falklands, indicating former greater 
extent of the land. 
Former greater extent of the land (Eocene-Miocene) in the Coronel-Lota 
region of Chile. 
