EDENTATA. 499 



animals which are exclusively confined to South America, in- 

 habiting the vast primaeval forests of that continent. The Sloths 

 have a remarkably short and rounded face, and the body is cov- 

 ered with hair. The incisor teeth are altogether wanting, but there 

 are always simple molars, and in the Two-toed Sloth or Unau the 

 first tooth in each jaw on each side is so much larger than the 

 others, and so much more pointed, that it has been regarded 

 as a canine. The stomach is complex, somewhat resembling 

 that of the Ruminants. The cervical vertebrae are generally 

 regarded as being more than the normal seven in number in the 

 Two-toed Sloth, and the long bones have no medullary cavi- 

 ties. The most striking peculiarities, however, about the 

 Sloths are connected with their peculiar mode of life. The 

 Sloths, in fact, are constructed to pass their life suspended 

 from the under surface of the branches of the trees amongst 

 which they live ; and for this end their organisation is singularly 

 adapted. The fore-limbs are much longer than the hind-limbs, 

 and the bones of the fore-arm are unusually movable. All the 

 feet, but especially the fore-feet, are furnished with enormously 

 long curved claws (fig. 190), by the aid of which the animal is 

 enabled to move about freely suspended back-downwards from 

 the branches. Not only is this the ordinary mode of progres- 

 sion amongst the Sloths, but even in sleep the animal appears 

 to retain this apparently unnatural position. 



Fig. 190. Hand of Three-toed Sloth (Bradyfius tridactylus) after Owen. 



Owing to the disproportionate size of the fore-limbs as com- 

 pared with the hind-limbs, and owing to the fact that the hind- 

 feet are so curved as to render it impossible to apply the sole 

 to the ground, the Sloth is an extremely awkward animal upon 

 the ground, and it has therefore recourse to terrestrial progres- 

 sion only when absolutely compelled to do so. Whilst the 



