May, 1913. New PEeruviAN MamMats — Oscoop. 99 
headwaters of Utcubamba River). No. 19724 Field Museum of 
Natural History. Adult male. Collected May 26, 1912, 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 10.8 x 2.8; 
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 takén 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. 
