4 ANIMAL COMPETITORS 
spread all over the continent, except the Utah 
basin. 
2. The black rat (Mus rattus), smaller than 
the ‘brown rat, and sooty or slaty black, paler 
on the under parts. Like the brown rat, it 
is of Oriental origin and seems to have pre- 
ceded the former in its immigration into 
western Europe and thence to this continent. 
It was carried from Europe to Spanish Amer- 
ica about three and a half centuries ago, and 
thence spread northward to the English col- 
onies. Upon the arrival of the brown rat in 
North America toward the end of the 18th 
century it began to decrease, and is now rare, 
surviving only in scattered colonies, but re- 
main numerous in many parts of the West 
Indies, Middle and South America, Hawaii, 
ete. 
3. The roof-rat (Mus alexandrinus), simi- 
lar to the brown rat in form and habits, but 
grayer above, and yellowish white on the feet 
and abdomen. Its history is much like that of 
the black rat, but it has held its own better 
against the dominance of the brown rat, in- 
habits sea-going ships, and has established 
