208 VIEW OF THE FAUNA OF BRAZIL 



having been a burrower. The next point to be considered 

 is the construction of the arm, which is invariably short 

 among buiTowing animals, as, indeed, theory would have led 

 us to expect. Now", in both the Megalonyx and Megathe- 

 rium the fore-limbs are long, even longer than the hind ones, 

 which is only the case with some apes, and the sloths ; these 

 two being, above all other mammals, the best climbers. 

 Next, in the conformation of the hind feet, we find strong 

 marks of distinction between burrowers and climbers ; for 

 instance, in moles the hind feet are remarkably weak in com- 

 parison with the fore-feet, and there is nothing extraordinary 

 in their structure. So also in those powerful burrowers. Da- 

 sypus gigas, and Das. gymnurus, we observe in these parts 

 the same conditions obtaining ; in none of that family is 

 there anything uncommon as to their construction. 



Now, it is easy to see that the hind feet could be but of 

 very little use to animals intended to burrow : but very dif- 

 ferent is the case with those intended for climbing. Not only 

 must the hinder extremities afford firm support to the body, 

 while the creature is climbing up, but often must they be 

 entrusted with its entire weight ; for instance, when it is 

 seeking for points of attachment for its fore-claws. Exactly, 

 therefore, as in the burrowers the main strength is placed in 

 the fore, so in climbing animals is it in the hinder extremities. 

 For this reason, we often see the hand in apes without an 

 opposable thumb, or with only a rudimentary thumb, or with 

 none at all ; while the thumb is always completely developed, 

 and perfectly opposed, in the hind feet. So, also, in other 

 families of climbers, w^e find the thumb constant on the hind, 

 while it is often absent from the fore feet ; and for the same 

 reason, the sloth is furnished with the same powerful claws 

 on the hind feet that we have already seen it to possess on the 

 fore feet. But both Megalonyx and Megatherium far exceed 

 all these animals in the extraordinarily powerful development 

 of their hind feet. The middle toe is disproportionately 

 strong, and is provided with so immense a claw, that w^e can 

 show nothing else like it in the whole animal kingdom; which 

 proves that these creatures must have used their hind feet for 

 some especial purpose. Their hind foot being furnished 

 with a single claw, shows that it was not intended for digging : 

 and the only analogy we can discover to it, is the single 

 strong claw that bats have on their anterior extremities, which 

 serves them to hang by. But much the most important cha- 

 racter in the foot of the Megalonyx is its oblique position 

 with relation to the leg, in consequence of which its sole 

 turns inwards instead of downwards. We have already seen 



