MAMMALIA 373 



Section 2. Myomorpha (Rat-like Rodents) . This is the largest mod- 

 ern group of mammals in point of numbers of species and of individ- 

 uals. At least a hundred genera and nearly five hundred species 

 have been distinguished. The group includes: dormice, field-mice, 

 rats and mice proper, mole rats, jumping mice (Fig. 192, C), and the 

 so-called African flying squirrels. They exhibit a very wide range of 

 adaptive specializations, being terrestrial, sub-terrestrial, arboreal, 

 cursorial and jumping, aquatic, and volant. They do serious damage 

 to the world's food supply and are responsible for the spread of some 

 of the worst plagues that Man has to contend with. 



Section 3. Hystricomorpha (Porcupine-like Rodents). This is a 

 somewhat heterogeneous group and is not very well described as 

 "porcupine-like," since many types appear quite unlike porcupines. 

 There are eight families, including: " water-rats," cavies, guinea-pigs, 

 agoutis (Fig. 192, E), chinchillas, ground porcupines, and tree por- 

 cupines. The cavies are South American and West Indian forms 

 that reach a length of four or five feet. They are terrestrial in habit, 

 with small ears and short tail. The chinchilla is a small squirrel-like 

 animal native to the Andes; the fur is soft and gray and is highly 

 prized. The Canada porcupine is a heavy-bodied terrestrial and 

 arboreal form that gnaws off the bark of trees, eats water-lily leaves 

 and roots. It is armed with short quills that are nearly hidden in the 

 long fur. Its equipment is purely for passive defense, except that it 

 lashes the tail and thus drives in its largest quills, when attacked. 

 Dogs are often injured when they are unwise enough to attack the 

 porcupine, for they get their mouths full of barbed quills that are 

 extremely difficult to remove. The European porcupine (Fig. 192, F) 

 is considerably larger than its American relative, having a body 

 length of about three feet. It has quills nearly a foot in length, those 

 on the tail being hollow so as to produce a rattling sound when the 

 animal is disturbed. A great crest of coarse hair surmounts the head 

 and hangs down like a mane. In spite of the prevalent reports to 

 that effect, the porcupine never shoots its quills. 



ORDER 6. EDENTATA (SLOTHS, ARMADILLOS, AND ANT-BEARS). 

 This group is believed to be a surviving remnant of an archaic group. 

 They have become highly specialized in several ways and exhibit 

 many evidences of racial senescence. The name of the order implies 

 a total lack of teeth and is therefore not appropriate for either the 

 armadillos or the sloths; the ant-bears alone are quite toothless. 



