obtained on the Rio Jordao. 531 
45. Tail finely haired, dark brown as usual, but the hairs 
of the underside are whitish, imperfectly hiding the brown 
scales. 
Skull with about the same snout-development as in 
O. nasutus, therefore much less than in the large Brazilian 
forms. Nasals about as wide anteriorly as at their middle, 
retroussé when viewed from the side, and extending posteriorly 
some way beyond the premaxillary processes. Interorbital 
region broad, smooth, and rounded. Outer wall of foramen 
magnum very narrow. Palatal foramina reaching back to 
the anterior third of m'; posterior edge of palate level with 
the back of m’*. 
Upper incisors very narrow. Molars with minute supple- 
mentary cusps in the valleys on the outer, but not on tie 
inner, sides. 
Dimensions of the type, measured in the flesh :— 
Head and body 127 millim.; tail 110; hind foot, s. u. 30, 
c. u. 33; ear 22. 
Skull: bregma to nasal tip 26; zygomatic breadth 15:3 ; 
nasals 13°7 x 4:5; interorbital breadth 6°7 ; length of anterior 
zygoma-root 2°4; palate length 13°6 ; diastema 8°3; palatal 
foramina 7°5 x 2°8; length of upper molar series 5°2. 
Type. Male. B.M. no. 1. 11.3. 51. Original number 
741. Collected 5th July, 1901. 
This species may be readily distinguished from any of its 
allies by its paler colour, without rufous above and _ less 
brightly buffy below. 
Of other South Brazilian species, I find that the true 
O. nasutus, Waterh., extends northwards from Uruguay at 
least into Rio Grande do Sul, in which province Dr. H. von 
Ihering obtained, besides the typical examples of O. Lhering/, 
Thos., specimens indistinguishable trom Darwin’s typical 
examples of 0. nasutus. 
15. Proechimys Robert, sp. n. 
Gg, 9 ¢- 
Closely similar externally to P. olivianus, described in 
the succeeding paper. Rather brighter and paler coloured, the 
general colour a richer fulvous, less heavily lined with black. 
Head not so conspicuously greyer than body. Under snr- 
face, inner side of limbs, and upper surface of hands and feet 
pure sharply-defined white. ail rather more hairy than in 
P. bolivianus ; brown above, whitish below. 
Skull smaller than that of P. bolivianus, about equalling 
that of P. Simonst. Nasal region long and narrow. Supra- 
ote 
