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 
all 
eZ “dt Be ee Mi 
a Nei) Sy. <N 
Cee an 
FIG, 350.—The lemming (ALyodes Jemmus), 
Zz 
Pa Fae 
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 (Arzicola) 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 
