178 THE FOOD OF ANIMALS 



in shape and structure. Thus, in Mammals, thorough-going 

 underground forms present more or less the features which are 

 familiarly embodied in the common mole. The body is com- 

 pact, the neck ill-marked, the tail reduced, and the limbs short 

 and strong. And further, the eyes and external ears are the 

 reverse of prominent, while the fur is short, thick, and velvety, 

 affording little resistance to the passage of the animal along its 

 burrow whether it moves forwards or backwards. All these 

 characters are presented by the Great Mole- Rat, and the much- 

 reduced eyes are in this case actually covered by a layer of skin. 

 The food consists of roots, bulbs, and the like. 



Porcupines {^Hystricomorphd) are mostly thick-set forms, dis- 

 tinguished by the development of a more or less complete array 

 of defensive quills, and with their cheek-teeth presenting grinding 

 crowns marked by folds of enamel. The species belonging to 

 the Old World live upon the ground, while those of the New 

 World are arboreal, and those of South America have prehensile 

 tails. 



Among the Cavy or Guinea- Pig Family (Caviidcs), all con- 

 fined to South America, the Capybara (^Hydrochcerus capybara) 

 may be mentioned as a very interesting type. It is the largest 

 living rodent, reaching the size of a small pig, and is of aquatic 

 habit, as might be suspected from the presence of short webs 

 between the toes of both fore- and hind-feet. But its most 

 interesting peculiarity is found in the structure of the cheek-teeth, 

 which have grinding crowns of far more complex nature than 

 those of other rodents, this being especially well-marked in the 

 case of the last members of the series, which resemble on a small 

 scale the grinders of an elephant. 



EDENTATES (Edentata) 



Amonof the archaic order of Edentates the Sloths of the 

 South American forests are purely herbivorous, feeding upon 

 the leaves, shoots, and fruits of the trees among which they live, 

 suspended upside down by means of long curved claws. Their 

 dull colour renders them inconspicuous, and the resemblance to 

 surroundings is increased by the presence of a minute alga which 

 grows on the stiff" hairs, and imparts a greenish hue. The neck 

 is very flexible, especially in the Three-toed Sloth {Bradypus) 

 (fig. 425), which possesses nine neck -vertebrae as against the 



