APRIL, 1914. MAMMALS OF NORTHERN PERU OSGOOD 161 



Rhipidomys fulviventer Thomas. BUFF-BELLIED VESPER RAT. 



Five specimens: Mountains east of Balsas at 10,000 ft. (i), 10 

 miles east of Molinopampa (i), Rio Utcubamba, between Leimabamba 

 and Chachapoyas (i), Tambo Almirante, near Uchco (2). 



There is some slight variation in this small series, probably due 

 mostly to age and condition of pelage. Specimens submitted to Mr. 

 Thomas are pronounced almost identical with the type. 



Oecomys bicolor (Tomes). 



One specimen, Tambo Yaku, near Rioja. 



Thomasomys praetor Thomas. 



Two specimens: Mountains near Otuzco (i), Hacienda Limon (i). 



Although one of these was taken at the edge of timberline and the 

 other well down on the side of the Maranon canyon, they seem to belong 

 to the same species. So far as known to me, they are the only specimens 

 of this species preserved except the type in the British Museum. Mr. 

 Thomas has compared one of them with the type, finding only such 

 differences as are likely to be due to disparity in age, the type not being 

 fully mature. Except for a short hind foot, the description of Thom- 

 asomys pyrrhonotus agrees fairly well with our specimens. 



Measurements of the adult are: Total length 387; head and body 

 187; tail 200; hind foot 38. 



Thomasomys cinereus (Thomas.) 



Twenty-three specimens, Mountains east of Balsas. Altitude 

 about 10,000 ft. 



The close agreement of these specimens with the original description 

 and the fact that the locality is relatively near that of the type leaves 

 scarcely any doubt of identity with T. cittereus, type species of the 

 genus Thomasomys. Like its congeners, it inhabits the depths of dense 

 humid forests. In the mountains where we found it, a heavy forest 

 was not well established except in certain narrow canyons where fog 

 and mist frequently settled while the surrounding peaks stood exposed 

 to the sun. In such places, it ranges practically to timberline but never, 

 so far as observed, beyond a growth of heavy moss, ferns, and rank 

 vegetation only to be found in cool shade. 



Adults and young differ but little in color and there is no great 

 variation in the color of the upper parts throughout the series except 



