APRIL, 1914. MAMMALS OF NORTHERN PERU — OsGoop 161 
Rhipidomys fulviventer Thomas. Burr-BELLIED Vesper Rat. 
Five specimens: Mountains east of Balsas at 10,000 ft. (1), 10 
miles east of Molinopampa (1), Rio Uteubamba, between Leimabamba 
and Chachapoyas (1), 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. ee 
Thomasomys pretor Thomas. 
Two specimens: Mountains near Otuzco (1), Hacienda Limon (1). 
Although one of these was taken at the edge of timberline and the 
other well down on the side of the Marafion 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 7. cinereus, 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 
tothesun. 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 
