new Rodents from the Orinoco and Ecuador. 370 



fulvous, passing gradually, without sharp line of demarcation, 

 into the colour of the belly, which is dull white, faintly 

 washed with buff. Throat, chest, and groins clearer white, 

 the hairs white to their bases. Arms and legs fulvous ex- 

 ternally, whitish internally. Hands and feet fulvous above, 

 gradually becoming browner terminally. Fifth hind toe 

 without claw reaching to the end of the first phalanx of the 

 fourth. Sole-pads broad, naked, obviously of the climbing 

 type. Tail fairly long, its basal three quarters of an inch 

 covered, as in most opossums, with longer fulvous fur similar 

 in character to that on the body ; the remainder shorter haired 

 than in most Rhipidomys, finely scaled, uniformly blackish 

 brown throughout. 



Skull in general shape much as in typical Rhipidomijs ; 

 back of nasals about level with ends of premaxillae ; supra- 

 orbital ridges well developed, evenly diverging backwards as 

 far as the middle of tlie parietals, then converging again to 

 the corners of the interparietal ; anteorbital plate of zygoma 

 little developed ; palatal foramina short, not reacliing back- 

 wards to m\ 



Molars of the squarish shape typical of Rhvpidomys, but 

 smaller than usual in proportion to the size of the animal. 



Dimensions of the type (an adult male, measured in the 

 flesh by collector) : — 



Head and body 124 millim. ; tail 157 ; hind foot (s. u.) 26 ; 

 ear 18. 



Skull: greatest length 34*2; basilar length 25*8; greatest 

 breadth 17-5; nasals ll'4x3"5; interorbital breadth 5"8 ; 

 interparietal 4*7 X 10 ; palate length from henselion 14'5 ; 

 diastema 8 9 ; palatal foramina 5*2 ; length of upper molar 

 series 5*2. 



Hob. Maipures, Upper Orinoco. 



%je B.M. no. 99. 9. 11. 38. Original number 11710. 

 Collected Jan. 22, 1899, by Geo. K. and Stella M. Cherrie. 

 One specimen only. 



Although apparently best placed in Rhipidomys, this inter- 

 esting rat shows considerable resemblance to Oryzomys by its 

 coarser fur and less hairy tail. 



Oryzomys auriventer, sp. n. 



A large dark species with a rich fulvous underside. 



Size rather less than in Mus rattus. Form delicate, the 

 limbs long and slender. Fur straight and fine, not soft and 

 woolly as in 0, aureus ] hairs of back about 10 millim. in 

 length. General colour above dark blackish fulvous, the 

 fulvous and black forming a coarsely lined mixture, especially 



