78 MOSTLY MAMMALS 



of their preservation is sufficiently accounted for by the 

 nature of the deposit itself. The marvel, however, is in 

 regard to the total disappearance of the whole of the larger 

 forms and the reduction of the fauna of the Pampas to its 

 present condition, together with the concomitant loss of 

 the forests. It is not that the country is unsuited at the 

 present day to the existence of the larger types of animal 

 life, as witness the countless herds of horses and cattle 

 with which its plains are now covered, together with the 

 luxuriance and rapidity with which many kinds of trees 

 flourish when introduced. Neither, I think, can it be due 

 to a glacial epoch (although there appears to be evidence 

 of the prevalence of a cold period in Patagonia), since any 

 glaciation of the Pampas would have assuredly removed the 

 greater part of the alluvial formation, besides having left 

 indisputable evidence of its presence. Man can scarcely 

 be credited with the extinction of either the fauna or the 

 flora. It has been suggested that the number of guanaco 

 with which the country was overrun previous to European 

 settlement may have caused the destruction of the forests ; 

 but we must remember that similar animals existed in 

 greater variety during the Pampean period, while even if 

 the disappearance of trees were due to their agency, this 

 would have had no effect on plain-loving forms like horses. 

 That the disappearance of the latter animals may have been 

 due to the number of pumas is another suggestion, but it 

 will be obvious that this could have had nothing to do with 

 the destruction of gigantic creatures like the glyptodons 

 and ground-sloths. The problem is further complicated 

 by the circumstance that the remains of many of these 

 creatures occur in caverns in the interior of Brazil, where 

 the climate is still, and probably always has been, tropical. 

 It would seem, therefore, that we must be content to regard 



