76 REPORT OF NEW JERSEY STATE MUSEUM. 
Too well known about houses, but often trapped, in summer 
at least, at long distances from houses, though in open farming 
districts. 
Mus musculus Abbott, Cook’s Geol. of N. J., 1868, p. 758.— 
Rhoads, Proc. Acad. Nat. Sci. Phila., 1897, p. 28.—Rhoads, 
Mam. Pa. and N. J., 1903, p. 218. 
Mus norvegicus Erxlebon. 
Norway Rat. 
PLATES 31 AND 26, Fic. 1. 
Length 18 inches. Heavily built, head thick, ears moderate, 
tail medium, shorter than head and body. Color yellowish 
brown, thickly interspersed with long black hairs, grayish white 
below. ‘Tail very sparsely haired with the scales very conspicu- 
ous, ears dull brown. Young dull gray with no brown tints. 
Abundant everywhere about the habitations of man and 
sometimes at some distance from them. The old ones slightly 
resemble the wood rat, while the half-grown young closely re- 
semble the rice-field mouse. The distinctions are pointed out 
under these species. 
The Norway rat seems to have everywhere exterminated or 
crowded out the black rat, Mus rattus, which was the first emi- 
grant rat to establish itself in many places. I know of no sur- 
viving colonies in the State. 
Mus decumanus Abbott, Cook’s Geol. of N. J., 1868, p. 758. 
—Rhoads, Proc. Acad. Nat. Sci. Phila., 1897, p. 28.—Rhoads, 
Mam. Pa. and N. J., 1903, p. 218. 
Family CASTORIDZ. 
THE BEAVERS. 
These curious animals are the largest North American ro- 
dents. They are thoroughly acquatic with a curious broad, flat 
tail and webbed feet. 
In the structure of their legs they belong nearer to the squir- 
rels than to the mouse tribe, having the bones of the lower legs 
separate and not fused together. 
