No. 479] 



EXTINCTION OF MAMMALIA 



783 



Decreasing Moisture. Secular Desiccaiiun 



Secular desiccation has been the fate of portions of three great 

 continents, and on each continent we observe a general concomi- 

 tant modification and extinction of certain kinds of quadrupeds. 

 The great regions of the world where decreasing moisture has 

 introduced a series of changes ending in the extinction of a great 

 number of quadrupeds are: 



(1) North America, Western Plains Region, Arid Plateau and 

 Mountain Region beginning in Oligocene times. 



(2) South America, Patagonia and Pampean Region, beginning 

 in late Pliocene times. 



(3) North Central Africa, the Faviim district beginning in 

 Oligocene times. 



(4) Central Australia, beginning in Pleistocene times. 



The writings of American paleontologists, also of Stirling, of 

 Andrews, and of Anicgin'no, describe fauna? adapted to much 

 moister coiiditioiis than diose which prevail at present. We 

 observe that decreasing nioisturo: 



(1) Changes the ehara.-ter of the food supply. Diminution of 

 softer and more MiecuhMit v.^uvtation. ineiva.e of harder and more 



(4) Jieduees iUv uater .iippK and eliniinaies aiiiinlu uieapable 

 of traveling long distances for food and watei'. 



(5) Favors grazing (juadrupeds and eliuiinares l)ro\vsing and 

 f orest-1 i vi ng ( j u adru peds. 



Prolonged or increasing droughts entirely disturl) tlie balance 



Carniv.)ra by drivinjthein ti> n-strieted water po..ls' They favor 

 quadrupe.U able to .li.pen.e ^^\tU a daily Mipply of ^^nrvv. 



of secular changes of climate on (piadriiped. are appare.itb .|nit<' 

 as important factors in extinction a> the direct, namely, chanuvs 

 in vegetation due to dimimition of moistni't". which render certain 



