252 



ZOOLOGY. 



The singular aard-Tark or Oryctcropns {0. capensis, 

 Fig. 292) iniiiibits South Africa, and is timid and nocturnal 

 I'n its habits, feeding on white ants. 



Order 2. Glires (Rodentia). — The rats, squirrels, porcu- 

 pine, and beaver are common examples of this extensive 

 group. They differ from animals of other orders in the 

 large incisor teeth and in tlie absence of canine teeth. The 

 feet are adapted for walking and climbing or burrowing, 

 the claws being long and curved. A ))eculiarity in the in- 

 cisors is that they grow out as fast as they are worn down; 

 this is due to the fact that the pulp is persistent; the 

 enamel in fi'ont causes them to wear away behind so that 



Fio. 292.— Oryctcropns. From Liltken's Zoology. 



they are chisel -shaped. The species are prolific, live mostly 

 on vegetable food, and are of small size; the muskrat, 

 beaver, and capybai'a being the largest members of the 

 order. The flying squirrels (Fig. 293) take short flights 

 by means of the expansion of the skin between the fore 

 and hind legs, gliding from tree to tree as if supported by 

 a parachute. They are only active at night. 



The Korway lemmings (Myodes) are noticeable for 

 their remarkable migrations from the elevated plateaus of 

 Scandinavia down and into the sea; the object and origin 

 of which are inex]ilicablo, and are not indicative of much 

 intelligence. While the true lemming has very small but 



