new Species of Oryzomys, &c. 537 
General colour above heavily lined fulvous brown, clearing 
into rich fulvous on the sides. Under surface dull white, 
fairly well defined ; the bases of the hairs slaty. 
Head greyer and duller above, but cheeks like sides. Hars 
large, well-haired, wholly dark brown, darker than the head. 
Outer side of limbs fulvous to wrist and ankles, inner sides 
white ; hands white, feet buffy white. Tail not or scarcely 
longer than the head and body, very finely haired and scaled, 
dull whitish below proximally, the upperside and end brown. 
Skull very similar to that of O. intermedius, with the same 
narrow muzzle, narrow interorbital region, weil-developed 
zygomatic plate, and medium-sized palatal foramina. But 
the molars are markedly smaller in all the specimens ex- 
amined. 
Dimensions of the type (measured in the flesh) :— 
Head and body 148 millim. ; tail 150; hind foot (s. u.) 34; 
ear 20. 
Skull: greatest length 345; basilar length 27; zygo- 
matic breadth 17°8; nasal, length 14; interorbital breadth 5; 
palate length 15 ; diastema 9°8; palatal foramina 6°5 x 2°8 ; 
length of molar series 4°6. 
Hab. (of type). Mapiri, Upper Beni River, Bolivia (about 
68° W. and 15°8.). Alt. 800 m. Other specimens from 
San Carlos (1200 m.) and Chimate (700 m.) in the same 
district. 
Type. Old male. B.M. no. 1. 1. 1. 64. Original number 
1203. Collected 29th August, 1900, by Mr. Perry O. Simons. 
Five specimens. 
In spite of the wide difference in locality between the 
habitats of O. bolivice and intermedius their resemblance to 
each other, both external and cranial, is so great that it is 
practically impossible to distinguish them except by the 
shorter tail and smaller molars of the new form. 
Proechimys bolivianus, sp. n. 
Most nearly allied to P. Simonsz, but larger and different 
in cranial details. 
Size as in P. brevicauda and the other large species. 
Spines about 19 millim. in length and 0°75 millim. in breadth. 
General colour paler than in P. Simonsz, fulvous, heavily 
lined with black, darker anteriorly, paler posteriorly ; a darker 
patch, as usual, on the middle of the rump. Head duller and 
ereyer than body. Under surface pure well-defined white. 
Hands and feet dull whitish, rather darker along their outer 
edges. Tail thinly haired, with large scales, slaty grey above, 
yellowish white below, 
