100 CALIFORNIA MAMMALS. 



Genus Mus Linn. (Mouse.) 

 Incisors narrow, not grooved in front ; tail long, nearly nak- 

 ed, the short sparse hairs not hiding the rings of scales covering 

 it ; ears rather large ; pelage usually harsh. 



Mus norvegicus Erxleben. (Of Norway.) 



BROWN RAT. 



Tail shorter than head and body; color above rusty brown 

 thickly mixed with coarse black hairs; sides grayer; below 

 ashy white; tail dusky, slightly paler below. 



Length about 400 mm. ( 15-75) inches) ; tail vertebrae 190 

 (7.50); hind foot 42 (1.65). 



Brown Rats were originally from central Asia, whence they 

 spread to Europe. They were incidentally introduced into Am- 

 erica in 1775. They have been known on the Pacific coast more 

 than fifty years, coming ashore from shipping and gradually 

 spreading through the country, but are yet unknown in many 

 parts of the State distant from large towns. They inhabit towns 

 preferably and are seldom seen far from buildings, in and under 

 which they find shelter. 



They are omnivorous and are great nuisances about barns, 

 warehouses and dwellings. They are hardy, courageous and 

 wary. They are more pugnacious than our native rats and soon 

 drive the latter away from their neighborhood. They are some- 

 times called Norway Rats and Wharf Rats. 



Mus rattus Linn. ( Rats . ) 



BLACK RAT 



Tail about as long as head and body ; above sooty black ; be- 

 low plumbeous; feet brown; averaging smaller than norvegicus. 



Introduced from Europe earlier than the Brown Rat, but 

 overpowered by the latter and now rare. The habits of the 

 two species are similar. 



