APRIL, 1914. MAMMALS or NORTHERN PERU OSGOOD 159 



These mice live in dense forest, where they seem to be generally dis- 

 tributed but difficult to obtain in numbers. A line of one hundred 

 carefully set traps in the forest seldom yielded more than two or three 

 specimens. They are limited strictly to the montagna region and our 

 westernmost record for them is Poco Tambo, where one specimen was 

 taken at an elevation of about 4,000 ft. 



They present a wide range of color variation, part of which evidently 

 is due to age, for all the individuals of strongly fulvous color are of large 

 size and fully mature. All mature specimens, however, are not of the 

 fulvous type, and it seems probable that there is in this species a limited 

 dichromatism. The length of the tail also is variable and, probably 

 by coincidence, all fulvous specimens have exceptionally long tails. 



Oryzomys albigularis (Tomes). WHITE-BREASTED ORYZOMYS. 



Eleven specimens: Tambo Almirante, near Uchco (4), Tambo 

 Ventija, near Molinopampa (5), Poco Tambo (2). 



The habitat of this rat was found to be the heavy humid forest of 

 the upper montagna from an altitude of about 5,000 ft. at least to 

 8,000 ft. Here it lives in the densest part of the forest under logs, 

 roots, and debris. In the absence of actual topotypes, our small series 

 may be regarded as representing true albigularis, the type of which 

 came from Pallatanga, Ecuador. It is rather darker than any of the 

 closely allied northern forms, the head being especially dark and the 

 tendency to the development of a blackish dorsal area being pronounced. 

 The under parts also are darker, and although some specimens have the 

 white pectoral spot well developed, others, especially the younger ones, 

 lack it entirely and have the whole under parts washed with fulvous. 

 The skulls of the Peruvian specimens are so similar to those of meridensis 

 that it is probable that form will eventually be regarded as a subspecies 

 of albigularis. The same may be said of maculiventer, pirrensis, and 

 devius. 0. childi, 0. o'connelli, and 0. pectoralis apparently should be 

 regarded as synonyms of meridensis. 0. keaysi differs from albigularis 

 more than any of the northern forms and intermediate specimens may 

 not be forthcoming. 



Oryzomys polius Osgood. GRAY ORYZOMYS. 



Six specimens, Tambo Carrizal, mountains east of Balsas. Altitude 

 about 5,000 ft. 



This very distinct species, apparently unrelated to any previously 

 known, is perhaps confined to the lower Maranon valley, like certain 



