no THE TAUNA OF 



offering some analogy to the stiff tail of the wood- 

 pecker (p. 47), which has the same function. 



We l^ave already spoken of the Canadian porcupine 

 (p. 43) in the taiga. This is represented in the 

 tropical forests of Mexico and Brazil by the tree- 

 porcupines of the genus Syntheres, which present 

 some interesting adaptations to arboreal life. The tail 

 is markedly prehensile, and the hind-foot is so inserted 

 as to make it easy for the animals to grasp the branches. 

 The great toe is absent, but its place is taken function- 

 ally by a fleshy lobe which can be bent inwards so 

 as to be partially opposed to the toes. The animals 

 are stated not to drink, and probably do not descend 

 voluntarily from the trees (see Fig. 30). 



We have already repeatedly emphasized the fact 

 that ungulates in America are few, and that their place 

 in nature is taken there by rodents ; there is, therefore, 

 nothing surprising in finding that the rodents called 

 agutis (Dasjrprocta) haunt the forests of Brazil and 

 elsewhere, and have become adapted for life in the 

 dense jungle. With their slender limbs and bodies 

 they show a close, though entirely superficial, resem- 

 blance to the chevrotains of South-East Asia. The paca 

 (Coelogenys) has similar habits. 



With the Edentates we come to a primitive order, 

 whose members have kept their hold in a world which 

 has grown beyond them either by retiring to the depths 

 of the tropical forests, or by acquiring burrowing and 

 concealed habits. In the forests of the Amazon occur 

 the sloths, belonging to the genus Bradypus and 

 Choloepus, perhaps the most truly arboreal of all 

 mammals, for they are quite helpless if removed from 

 the trees among which they pass their whole lives. 

 The fact that they possess practically no adaptation 



