364 ORIGIN OF LIFE IN AMERICA 



struggle for life among animals as well as among plants. 

 And yet, except birds, insects and lizards, animals do 

 not appear to be present in unusually large numbers. The 

 large class of mammals, which elsewhere form such a con- 

 spicuous feature of a fauna, seem almost to be absent. This 

 is largely due to the fact that Brazil is really poor in terrestrial 

 mammals. Those that do inhabit the country are chiefly of 

 arboreal habits, and thus escape attention. Mr. Bates * 

 believes that the South American fauna has been slowly 

 adapted to an arboreal life, and that extensive forests 

 must always have existed since the region was first peopled 

 by mammalia. 



Among these arboreal mammals the family of the capuchin 

 monkeys (Cebidae), whose unusually prehensile tail gives 

 them peculiar facilities for climbing, are the most noteworthy. 

 They range all over tropical America, being most abundant 

 in the dense forest regions of Brazil. In some monkeys, like 

 the howlers (Mycetes), the end of the tail underneath is devoid 

 of hair, and thus acts with even greater efficiency than in 

 capuchins (Cebus). The sakis (Pithecia) and squirrel-mon- 

 keys .(Chrysothrix) have non-prehensile tails. The spider 

 monkeys, with their long limbs and long prehensile tail, are 

 the most admirably adapted creatures for a purely arboreal 

 life. A second family (Hapalidae) includes the smallest of all 

 monkeys, the marmosets. Mostly very active little squirrel- 

 like creatures, with arboreal habits, they are almost confined 

 to Brazil and north-western South America. In many respects 

 these two families of South American monkeys are closely 

 related to one another, whereas they differ from the Old World 

 species, especially in their dentition. Since no members of 

 the Cebidae and Hapalidae have ever been found fossil outside 

 South or Central America, it is believed that they form a 

 branch distinct from the Old World monkeys, having had a 

 separate origin from lemur-like creatures. Dr. Ameghino has 

 described quite a number of lemuroid remains from the Cre- 

 taceous of Patagonia, and he maintains that these early fore- 

 runners of monkeys and man originated in the ancient vast 

 territories of southern South America. I am fully aware that 



* Bates, H. W., "Naturalist on the Amazons," p. 32. 



