324 BACKBONED ANIMALS. 



the globe. The upper lips are divided, the snout acute, 

 and the ears generally naked. The Bandicoot rat is the 

 largest, attaining in India a length of fourteen inches. The 

 Norway rat attains a length of eight or ten inches, and is 

 of a rusty brown color. They are very intelligent and 

 prolific. They came originally from Central Asia, appear- 

 ing first in Russia in 1737, crossing in vessels to America 

 in 1775. This is the ordinary wharf rat. The black rat 

 emigrated to this country in 1544. The musk-rat is an 

 aquatic form, with a flattened tail and webbed hind-feet, 

 that forms huts of grass and roots under water, and tun- 

 nels in the bank. The coypu (Fig. 349), of the Chonos 

 archipelago, is an allied form, also common in the streams 



FIG. 350. The lemming (Myodcs lemmus). 



of South America. The house mouse is an importation 

 from Europe and Asia. The European harvest mice (Fig. 

 345) are noted as nest-builders, forming them by weaving 

 spears of grass about stalks of grain. The American field 

 mouse (Arvicola) nests under ground in spring, on the 

 surface in midsummer, and on the surface beneath the 

 snow in winter. It does not hibernate. The lemmings 



