134 TEXT-BOOK OF ZOOLOGY 



When alarmed, they immediately roll themselves into balls like the 

 hedgehog, so that the sharp edges of the scales are presented. The 

 plates overlap like the tiles of a roof, and are formed of united hairs. 

 The armour thus forms an effective protection for the slow and inoffensive 

 creature. The lower side of the body is covered only with ordinary hair. 

 A similar armour is possessed by the Armadillos (Dasypus), which live 

 in South and Central America ; the skin of the back is modified into 

 movable rings or girdles consisting of plate-like shields, each containing 

 a plate of bone, as in some reptiles. The teeth are numerous, but very 

 weak, and the animals further protect themselves by burrowing with 

 their powerful claws into the ground. There, also, they find their food, 

 which consists chiefly of insects. 



ORDER XIII. : MARSUPIALS (MARSUPIALIA). 



Animals provided with an abdominal pouch, or marsupium, in which 

 are contained the nipples of the mammary glands, and in which the 

 young are suckled during their early, imperfectly developed, condition. 

 The abdominal wall is supported by two so-called marsupial bones. The 

 teeth vary in number and shape, according to the kind of food (conform- 

 ing to the carnivorous, insectivorous, herbivorous, or rodent types). All 

 the marsupials are limited to Australia and America. 



The Great Kangaroo (Macropus giganteus). 



This animal is an inhabitant of the Bush and the grassy plains of 

 Australia. Its ordinary mode of progression is by a series of leaps and 

 bounds. In accordance with this habit, the hind-limbs, as in all other 

 leaping animals (e.g., hare, grasshopper, flea), much exceed the fore- 

 limbs in length and strength. This mode of progression, however, calls 

 forth a considerable amount of bodily force, which has its seat in 

 the muscles of the thigh. Moreover, the posterior portion of the body 

 is of remarkable size and strength as compared with the small head 

 and the chest. In taking a leap, the animal uses especially its middle 

 toe, which is very long and carries a powerful claw, as a prop or support 

 against the inequalities of the surface (this middle toe, in the absence 

 of a thumb and the concrescence of the second and third toes, corre- 

 sponds to the fourth toe in the human foot) ; it then, by exercising 

 pressure on the elastic hind-legs, is jerked upwards and flies like an 

 arrow through the air. "When suddenly alarmed, the animal can execute 

 a leap of more than 33 feet. In its leaps it clears bushes as well as 

 ravines, so that in mountainous or wooded districts even the quick-footed 



