396 ORIGIN OF LIFE IN AMERICA 



we proceed southward, the fauna and flora gradually undergo 

 a complete change. On leaving the forest, monkeys, sloths 

 and other animals, bound to an arboreal life, are replaced by 

 new types, unknown in Brazil, such as the Patagonian hare 

 and vizcacha. A very characteristic faunistic feature of the 

 Argentine " pampas," as the humid grassy country is called, 

 is the presence there of the American representative of the 

 ostrich. This rhea is quite absent from the vast forests of 

 Brazil. In the northern parts of that country, however, where 

 we again meet with grass lands, this flightless bird reappears 

 as a memento of the times when north and south were joined 

 by continuous prairies. We thus have some noteworthy 

 instances of discontinuous distribution suggesting a former 

 period when the drying up of vast lakes, perhaps, may have 

 given rise to grass lands, which enabled certain southern types 

 to push northward. Other Argentine animals, such as the 

 coypu (Myocastor coypus) , one of the largest of the rodent 

 tribe, have apparently invaded Brazil in more recent times, 

 for they have only entered the southern and western pro- 

 vinces. To those unacquainted with the past history of South 

 America it must come as a matter of surprise that the only 

 ungulate which is noticed in these vast pampas of Argen- 

 tina is a deer, closely related to the true North American deer 

 (Odocoileus virginianus) and its allies. I have expressed my 

 belief above (p. Ill) that the true American deer owe their 

 origin to one or more ancestors which passed into South 

 America directly from Europe, and it is important to note 

 that the centre of dispersal of the various groups in South 

 America lies in the western states. Only a couple of species 

 are peculiar to Brazil. All the others are more or less 

 confined to the western states. Even the distribution of the 

 South American wolves led Dr. von Ihering * to the similar 

 conclusion that these animals entered the continent from the 

 west. 



Mr. W. H. Hudson f gives us a vivid idea of the life in the 

 pampas of Argentina, the striking poverty of its fauna as 

 compared with Brazil, and all the more characteristic features 



* Ihering, H. von, " Stidamerikanische Raubtiere," p. 162. 

 t Hudson, W. H., ." Naturalist in La Plata." 



