366 
ORIGIN OF LIFE IN AMERICA 
supported by the long claws of its toes. Two genera of this 
edentate mammal are known, viz., Bradypus and Choloepus, 
both of them confined to South and Central America, and, like 
the monkeys, absent from Argentina, Chile and Patagonia. 
In spite of their absence from the latter country, it is there, 
according to Dr. Ameghino, that we find the earliest traces 
of the sloth-tribe in the Eocene beds. The Eocene Entelops 
and Trematherium have been placed into the same family 
with the modern sloths. Certain sloth-like remains have even 
been traced back to the Upper Cretaceous of Patagonia. 
Sloths of the arboreal type have not been found fossil out¬ 
side South America. The remains of a supposed sloth (Brady- 
therium) were discovered by Mr. Grandidier ten years ago 
on the island of Madagascar. According to Dr. Smith Wood¬ 
ward they belong to a lemur, yet there are so many other 
points of affinity between South America and Madagascar 
that a former direct land connection between the two regions 
has been suggested. I return to this subject more fully in 
the next chapter. 
In a previous chapter (p. 70) I explained that, although 
all American porcupines are arboreal in distinction to the 
Old World species which live on the ground, only the 
South and Central American forms have prehensile tails. 
This gives them greater facilities for dispersal in Brazil, and 
greater protection from their enemies. These South 
American porcupines agree in their general range with the 
monkeys and the sloths, and like them are absent from the 
southern states of South America, although their ancestral 
home was seemingly in Patagonia. Some species of Coendu 
are known from the Brazilian caves, still, the centre of origin 
lay manifestly further south. 
Of the pouched or marsupial mammals we have noticed that 
the opossum has a wide range in North America. In Central 
and South America the same North American species 
(Didelphys marsupialis) occurs widely distributed. Such an 
enormously extensive range must be due to the fact of its 
being a persistent mammalian type. The genus, or one 
closely related to it, certainly was already represented in the 
Lower Eocene of North America and the Upper Eocene of 
France. Only one genus of these marsupial mammals occurs 
