668 MAMMALIA [CH. 



their natural surroundings. It is then seen that one family, the 

 Sloths (BRADYPODIDAE), spend all their time climbing about on trees, 

 on the leaves of which they feed. There is a remarkable adaptation 

 which probably helps them to escape detection by their enemies. 

 The surface of the hairs is grooved and affords a resting-place for a 

 unicellular Alga which causes the animal to have a greenish appear- 

 ance so as to be almost invisible amidst the foliage. The second 

 family include the true Ant-eaters or MYRMECOPHAGIDAE ; in these 

 the strong claws are used for pulling down and digging up ant-hills. 

 The muzzle is long and toothless. There is a very long tongue, 



FIG. 335. White-bellied Pangolin, Manis tricuipis. 



and enormous salivary glands, the sticky secretion of which entraps 

 the ants. The Tamandua Ant-eater, Tamandua tetradactyla, of 

 Central and South America, is arboreal in its habits and lives in the 

 dense primeval forests of the New "World : it uses its strong 

 claws for climbing and has a prehensile tail. The third family, 

 the Armadillos or DASYPODIDAE, can dig with such rapidity that a 

 comparatively large animal will scoop out a burrow for itself in a 

 few minutes. These Armadillos are also very remarkable as being 

 the only Mammals in which the dermis or deeper skin develops 

 into hard bony plates like the osteoderms of Reptilia, whilst the 



