438 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL EEPORT. 
MUS DECUMANUS, Pallas. 
Norway Rat--- Brown Rat. 
Mus decumanus, Pauwas, Glires, 1778, 91. 
Scureser, Saugt. IV, 645; tab. clxxviii. 
KeyseRLING und Brasius, Eur. Wirb. I, 1842, 36. 
DeKay, N. Y. Zool. I, 1842, 80. 
Waener, Suppl. Schreb. III, 1843, 1. 
Burmeister, Thiere Brasiliens, I, 1854, 152. 
Aup. and Bacu, N. Am. Quad. II, 1851, 22; pl. liv. 
Mus norvegicus ERXiEBEN, Syst. An. I, 1776, 381. 
Norway Rat, Pennant, “ British Zoology.” 
Brown Rat, PENNANT, ‘‘ Synopsis Quadrup.”’ 
Sp. Cu.—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 UW. 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 Jf. 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. 
Inches. Lines. 
INOS@ SLO GCCIDN t= ees eee tee ene 1 | 9 
FA ae Se Sen CEO Se Se recs Seen 83 
(es eset See ae oe Se CESS ease Sce 1 4 
TOYO) TO} EI i ee 6 5 
end of outstretched hind legs ------------ 7 eaccceaee 
Tail, from root to end of vertebre.--------------- 5 9 
EN ee ae ae 5 9 
naked portion-..-------- t 1l 
Mar, heightiposteniorly— 2.2 — <= cee ee mene an |e i 9 
anteriorly -.-.-..---.------=--=---=-|-==------- 7h 
internally above 'skull_—<-__.<_-_--.- - S|" ae 
BDOVE NOtCh onan sees eae eee eee eee eee 8 
width in natural position -.--.-.------|---------- 64 
Arm, from elbow to end of claws-- ------ --------- 1 8 
forefoot to end of claws.-.-.-------- B93 5-|15 Sao 9 
longest /claw =<. .= 2c see= ones eb een eeee eer a|eeoe hese i 
Leg, from knee joint to end of claws-------------- 2 6 
HDIG ooo poe ts ces owen een Conese nemee ae 1 4 
hind foot from heel to end of claws -.-------- 1 6 
LORP EB CIAWE = eee oa eee ee eal om am ee 2 
Annuli of tail 190 to 200. 
