THE PLEISTOCENE OR GLACIAL PERIOD. 



501 



luxuriance of this great fauna really antedated the congestion attendant 

 on the maximum extension of the ice, and that the extinction of the 

 giant edentates, which seems to have followed their abundance some- 

 what closely, was connected with this extension. If this were true, 

 the fauna would be referred to the Pliocene and the earliest stages of 

 the Pleistocene and not to the later or true glacial Pleistocene. 

 Question as to current reference is perhaps warranted by the extreme 

 difficulty of closely correlating widely isolated formations in a transi- 

 tion period like the Pleistocene. 



Fig, 563. — A club-tailed glyptodont, Doedicurus clavicaudatus, from South 



(After Lydekker.) 



America. 



Australian life. — Owing to the isolation of Australia from the 

 Eurasian continent, its organic development followed lines of its own. 

 The vertebrate fauna consisted exclusively of marsupials and mono- 

 tremes. In general, they differed specifically from those now living, 

 and were larger, on the whole. The subsequent dwarfing was pos- 

 sibly due to the less genial climate of the ice age, and is perhaps to 

 be correlated in time as suggested above. Although the glaciers were 

 but slightly developed on the Australian mountains, the region doubt- 

 less felt the effects of the wide-spread refrigeration of the higher lati- 

 tudes, and of the aridity which seems to have accompanied some of 

 its stages. 



Life in Africa. — Comparatively little is known of the Pleistocene 

 life of Africa. A moderate climate in the northern portion seems 



