AND DESERTS 135 



to cold or wet. Another species is found in Bolivia. 

 The members of the type genus Dasjrpus are widely 

 distributed, being especially common in the Argentine. 

 In addition to the protective covering of bony plates, 

 they find security from their enemies in their burrow- 

 ing habits, and in the fact that they are mostly noc- 

 turnal. 



In Africa, where armadillos are completely absent, 

 another curious edentate, the aard-vark or ant-bear 

 (Orcyteropus) occurs in open regions, and is also of 

 burrowing nocturnal habits, though it has no armour 

 as the armadillos have. It seems to feed chiefly on 

 termites, the so-called white ants. 



Of the marsupials the kangaroos and their immediate 

 aUies are exclusively confined to the Australian region, 

 and there they formed the natural fauna of the savanas 

 tiU the advent of the European with his flocks and 

 herds. The kangaroos and wallabies, with the excep- 

 tion of the tree-kangaroos already mentioned, are 

 ground forms, feeding not only upon grass but also 

 upon shoots of bushes and shrubs, or even in the case 

 of the larger forms, on leaves, &c., of trees, which they 

 reach by standing in the upright position. The tail is 

 long and strong. It aids the animal in maintaining 

 the upright position, and also in running — ^that is, in 

 leaping. We have already noticed the essential points 

 of structure in the kangaroo ; the elongation of the 

 hind-hmbs, without corresponding elongation of either 

 forehmbs or neck, is an adaptive pecuharity which is 

 far from uncommon in animals of the open plains. In 

 the ungulates the other type of adaptation, that which 

 consists in the elongation of both pairs of limbs, and 

 therefore necessarily of the neck to permit feeding to 

 take place, is the usual one. Just as among the rodents 



