May, 1913. New Peruvian Mammals — Osgood. 99 



headwaters of Utcubamba River). No. 19724 Field Museum of 

 Natural History. Adult male. Collected May 26, 191 2, by W. H. 

 Osgood and M. P. Anderson. 



Characters. Similar in color and character of pelage to Akodon 

 mollis altorum, but averaging slightly larger and more fulvous and having 

 marked cranial characters. Skull compressed and attenuate anteriorly; 

 nasals slender and elongate; zygomatic plate short, having its anterior 

 edge convex and receding from the base ; braincase broader and more 

 smoothly rounded than in mollis and altorum; temporal ridges practical- 

 ly obliterated. 



Measurements. Type: Total length 192; head and body 107 

 tail 85; hind foot 23. Skull: Greatest length 26.8; basal length 24.5 

 zygomatic breadth 13.3; interorbital breadth 4.9; nasals 10.8x2.8 

 palatine foramina 5.8; diastema 6.8; upper molar series 4.4. 



Remarks. From examination of an extensive series of specimens 

 representing localities from the Pacific coast to the lower slopes of the 

 eastern Andes of northern Peru, it is evident that Akodon mollis is 

 divisible into four easily recognized forms. The division is primarily 

 by cranial characters and secondarily by color. Typical mollis of the 

 coast region and altorum of the western Andes differ somewhat in color 

 and pelage but have the same type of skull as contrasted with orophi- 

 lus of the central Andes and orientalis of the upper montagna region, 

 these latter being likewise differentiated by color and dimensions. 

 Ecuadorean specimens of altorum are not at hand, but the statement in 

 the original description^ that they are cranially "as in true mollis '^ 

 is taken as sufficient evidence that they do not differ from specimens 

 from the western Andes of Peru (Cajamarca, Otuzco, etc.). 



Akodon mollis orientalis subsp. nov. 



Type from Poco Tambo, between Chachapoyas and Rioja, Peru. 

 Altitude about 6000 ft. No. 19855 Field Museum of Natural History. 

 Adult female. Collected June 29, 1912, by W. H. Osgood and 

 M. P. Anderson. 



Characters. Similar in cranial characters to A. m. orophilus but 

 larger, longer-tailed, and much darker in color. Upper parts deep 

 mummy brown in general appearance, the hairs annulated with dark 

 umber and tipped with blackish ; under parts heavily washed with tawny 

 russet; tail and feet entirely blackish. Skull of the same general form 

 and having the slender rostrum and short receding zygomatic plate as 

 in orophilus, but braincase slightly broader and more ample. 



1 Thomas, Ann. & Mag. Nat. Hist., (8), xi. p. 404, April, 1913. 



