No. 416] MAMMALS IN SAN MIGUEL ISLAND. 641 
Color and Pelage: Spines confined to anterior two-thirds of 
back (as in all members of this group of the genus); spines 
not particularly numerous (as is the 
case in cAzrzquzmus), but well covered 
by the hair ; whole upper parts rich, 
deep, ferruginous, slightly varied along 
back by the brownish-black tips of the 
spines showing through the hair; top 
of nose, cheeks, and lower sides a 
little paler, more yellowish; under 
parts pure white, except anal region 
and base of tail, which are colored 
like the back ; hands and feet dusky 
brown, in some specimens slightly 
grayer along inner edge of metatar- 
sus; tail bicolored, black above, gray- 
ish below, well clothed with short, tyre ot Proechimys burrus, adult d - 
stiff hairs ; ears dusky, nearly naked. 
Young examples, half grown, are much darker, less reddish 
above ; but among the adults there is little variation in color. 
MEASUREMENTS. 
| | Bas FROM 
NuMBER. Sex. DATE. Neal | Gina bi. | Norcu. 
8458, type $ adult | April 3o | 470 185 58 23 
8448, topotype | d. « u 21| 490 205 et 
8455, “ Pow "9 470 165 54 as 
8449, “ ee “24 470 165 58 21 
8451, “ 4 on “ 22 460 180 58 21 
8450, « A ow “ 27 440 160 58 ne 
8459, « 9 « “ 21 425 150 52 " 
8454, “ erik “ay 438 165 2 22 
8456, “ 9 “ “ 24 410 145 50 | 20 
8460, « $ May 5 | 400 140 ow" 
Skull, type, adult 4, basal length, 52; occipito-nasal length, 
1.2; zygomatic width, 29; mastoid width, 22.2; least inter- 
orbital width, 13.4; length of nasals, 24.2; width of nasals, 
