144 



We have then further to interrogate the remains of this extraordinary gigantic 

 Sloth for more definite information as to the mode in which it obtained its food. 

 The answers which the osteological characters of the fore-limb have yielded are 

 valuable, as we have seen, rather for their negation of erroneous conjecture, than 

 for the truths which they directly affirm. Reference must therefore be made to 

 the organization of the hind-limbs to ascertain whether any light may thence be 

 reflected on the functions of the fore-feet and on the general habits of the Mylodon. 



In existing Mammals the modifications of the pelvis and hind-limbs are well- 

 marked and highly characteristic of the strictly burrowing and climbing species. 

 The whole or chief part of the digging actions is performed by the fore-feet in 

 the best burro wers, the Mole for instance ; the pelvis and hind-feet being re- 

 markably slender and feeble in that animal, and presenting no notable develop- 

 ment or structure in the less powerful or less habitual excavators. In the 

 best climbing animals, such as the Sloths and Orangs, the hind-legs are much 

 shorter than the fore-legs ; and in all climbing animals, in which the hind-feet 

 are endowed with a more or less perfect power of grasping, this is never com- 

 bined with excessive bulk and weight of the limbs themselves, or of the hinder 

 parts of the body, not even in those species in which a prehensile tail is super- 

 added, as it is in the American Spider-monkeys. Certain small Kangaroos (Den- 

 drolagus, Miiller), which by a curvature of the long claw of the hind-foot are 

 enabled to spring up the trunk and thus attain the branches of trees, form no 

 exception to this rule, since their organization is essentially saltatorial, although 

 by a slight modification this power may be exercised in a different sphere than 

 that of the surface of the earth. The terrestrial Ant-eaters offer nothing ex- 

 traordinary in the size or structure of their hind-limbs : the arboreal species are 

 distinguished by the inferior size of these members. 



When, therefore, after a re^^ew of the pelvis and hind-limbs in existing scan- 

 sorial, fossorial, or semi-fossorial quadrupeds, we turn to the contemplation of the 

 same parts of the skeleton of the Mylodon or Megatherium, the sudden and ex- 

 traordinary increase of size, and the massive proportions which meet the eye, 

 and arrest the attention of the most indifferent beholder, become eminently sug- 

 gestive to the physiologist and clearly imply powers and actions as peculiar to 

 the gigantic animals when living, as are the modifications of these most striking 

 parts of the enduring framework of their long since decomposed bodies. 



The enormous pelvis of the Mylodon proclaims itself the centre whence mus- 



