FIELD BOOK OF MAMMALS 



showing as low ridges rather than distinct tubercles) and no 

 Mouse or Rat native to North America has molars with these 

 three rows. 



Genus Rattus 



Dentition: Incisors, {; Canines, §; Premolars, ^; Molars, f = i6. 



Norway Rat. — Rattus norvegicus 



(Best known in literature as Mus norvegicus). Plate XXXIII. 



Names. — Norway Rat; Common Rat; House Rat; Wharf 

 Rat; Barn Rat; Gray Rat; Domestic Rat; Brown Rat. 



General Description. — A good-sized Rat, with large, nearly 

 naked, ears; long, semi-naked tail, with rather conspicuous 



Fig. 93. Norway Rat 



annulations ; pelage somewhat coarse ; brown or grayish above, 

 ashy below. 



Color. — Sexes colored alike, no noticeable seasonal 

 variation. 



Upperparts. — Grayish or brownish, with mixture of more 

 or less black; feet grayish or whitish; tail not distinctly bi- 

 color, dusky above, somewhat lighter below. 



Underparts. — Grayish to soiled whitish; transition in color 

 from sides to underparts gradual. 



Immature pelage duller and grayer than adult. 



Measurements. — Sexes of equal size. Total length, 15-16 

 inches; tail vertebras, 7-8 inches; hind foot, 1.6- 1.7 inches. 



450 



