438 



U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL EEPORT. 



MUS DECUMANUS, Pallas. 



Norway Rat Brown Rat. 



Mtu dccumamu, PALLAS, Glires, 1778, 91. 



SCIIBCBEB, Saugt. IV, 645 ; tab. clxxviii. 



RETSKRLIXG und BLASITJS, Eur. Wirb. I, 1842, 36. 



DEKAY, N. Y. Zool. I, 1842, 80. 



WAGNEB, Suppl. Schreb. Ill, 1843, 1. 



BCBMEISTEB, Thiere Brasiliens, I, 1854, 152. 



AUD. and BACH, N. Am. Quad. II, 1851,22 ; pi. liv. 

 J/fut norvegicus EBXLEBEN, Syst. An. I, 1776, 381. 

 Norway Rat, PENNANT, " British Zoology." 

 Brown Rat, PENNANT, " Synopsis Quadrup." 



SP. CH. Tail about three-quarters of an inch shorter than head and body. Tail sparsely hairy, with about two hundred 

 annuli. Above, grayish brown, mixed with rusty ; grayer on the sides ; beneath, ashy white. Upper surface of the feet 

 dirty white. Body, 8 to 10 inches. 



The general peculiarities of head, feet, and tail, are as in M. tectorum. The tail is, however, 

 much shorter, being considerably less than the head and body. 



The upper parts are grayish brown, mixed with faint rusty, and darkened by black tipped 

 hairs ; the sides are grayer ; the belly and feet a light whitish ash, not so pure as in Neotoma 

 or Mus tectorum. The under surface of the tail is a little paler than the upper, which is dusky. 

 In the dried skin the annuli of the tail are much less distinct than in M. rattus and tectorum, 

 owing to the rather longer hairs. 



Specimens from Oregon appear to have the tail slightly longer than those from the east side 

 of the mountains. 



Measurements of a fresh specimen. 



Annuli of tail 190 to 200. 



