114 THE MAMMALIA. 



branches of trees, and the animals are, by a peculiar 

 arrangement in the circulation of their blood, en- 

 abled to remain hours and days in the most un- 

 comfortable positions ; hence they have almost com- 

 pletely lost the faculty of moving along level ground. 

 The nearest relatives of the Sloth i.e. of the 

 genera Bradypus and Clwlcepus are the colossal 

 Megatherium and Mylodon, found in the Diluvial 

 deposits of North and South America. Of the 

 former we have an account, with illustrations, in 

 E. d' Alton's * Classic Monographies,' where it is 

 called ' the giant sloth.' He there says, that, com- 

 pared with its skeleton of fourteen feet in length and 

 seven feet high, that of the rhinoceros appears grace- 

 ful, the elephant light and slim, and the hippo- 

 potamus of good proportions. Its unusually broad 

 and bulky body has a very small skull (Fig. 8), and 

 is remarkably like that of our present Sloth. True, 

 the cheek-bone, which in the case of the Giant 

 Sloth is firmly attached to the temporal bone, is 

 not thus joined in our present Sloth (Fig. 9), but 

 in the case of both the cheek-bone shows a strongly 

 developed continuation that points downwards. The 

 teeth of the fossil animal, sixteen in number, are 

 compressed within the actual region of the cheek ; in 

 the existing species they stand more apart ; but in 



