590 MANUAL OF ZOOLOGY. 



the Muridm, comprising the Rats, Mice, and Lemmings. In 

 this family the tail is long, always thinly haired, sometimes 

 naked and scaly. The lower incisors are narrow and pointed, 

 and there are complete clavicles. The hind-feet are furnished 

 with five toes, the fore-feet with four, together with a rudi- 

 mentary poUex. 



The Rats (Mus rattus and Mus dccumanus), the common 

 Mouse {Mus musculus), the Field-mouse {Mus sylvaticus), and 

 the Harvest-mouse {Mus messorius), are all well-known examples 

 of this family, and are too familiar to require any description. 

 The three first are also common in North America. Closely 

 allied to the true Rats are the Hamsters {Cricetus, fig. 229), and 

 the Voles {Arvicold) ; the latter represented by many species in 

 both Europe and America! 



A less familiar example of this family is the Lemming {Myodes 



Fig. 229. — Common Hamster {Cricetus vulgaris). 



lemmus). This curious little Rodent is found inhabiting the 

 mountainous regions of Norway and Sweden. It is chiefly re- 

 markable for migrating at certain periods, generally towards the 

 approach of"winter, in immense multitudes and in a straight 

 line, apparently in obedience to some blind mechanical im- 

 pulse. In these journeys the Lemmings march in parallel 

 columns, and nothing will induce them to deviate from the 

 straight line of march. 



Fam. 6. Dipodida. — The sixth family of the Rodents, which 

 is sufficiently important to need notice, is that of the Dipodidm 

 or Jerboas, mainly characterised by the. disproportionate length 

 of the hind-limbs as compared with the fore-limbs. The tail 

 also is long and hairy, and there are complete clavicles. The 

 Jerboas live in troops, and owing to the great length of the 

 hind-legs, they can leap with great activity and to great dis- 



