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. Hr. 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. 
