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 



