tLIFE 475 



uthcrn part of Hra/.il, and in Argentina. The associated coal 

 forma lions carry the same flora (glossopteris flora) as in the other 

 continents. 



In the northern hemisphere the glaciation is known to have 

 extended from latitude 18 to about 35, and in the southern, from 

 latitude 21 to 35. In an equatorial zone about 40 in width, 

 glaciation has not been discovered. The glaciation can hardly be 

 said to be limited in longitude. Glacial conditions must, therefore, 

 have prevailed about the borders of an area many times as large as 

 that covered by ice in the northern hemisphere during the Pleisto- 

 cene glacial period. 



The marked likeness of the floras associated with the glacial 

 deposits in these four continents is evidence that there was land 

 connection between them at the time of glaciation. The age of the 

 glacial beds is not absolutely established, for the Carboniferous 

 and Permian are not clearly differentiated in the regions where they 

 occur. Perhaps the best judgment that can be formed now is that 

 the Paleozoic glaciation. culminated in the early part of the Permian 



I period. 

 Close of the Paleozoic Era 



The close of the Paleozoic era was marked by much more con- 

 siderable geographic changes than the close of any period since 

 the Proterozoic, though they may be said to have been in progress 

 during the Permian period, rather than to have occurred at its close. 

 The more important changes in North America, which were far 

 advanced by the close of the Paleozoic, were (i) the development of 

 the Appalachian mountain system at the western border of Appa- 

 lachia; (2) the deformation of the surface of Appalachia; (3) the 

 development of the Ouachita Mountains; (4) the final conversion 

 of most of the area between the Great Plains and Appalachia from 

 an area of deposition to one of erosion; and (5) the restriction of the 

 area of sedimentation in the western interior. 



Such extensive geographic changes, involving the conversion of 

 extensive areas from sea bottom into land, must have caused pro- 

 found changes in the circulation of ocean waters, in the climate of 

 many localities, and in the distribution of life. 



LIFE 



The life of the Permian must be interpreted in connection with 

 the extraordinary physical conditions which formed its environ- 



