158 Fretp Museum or Naturat History — Zoétoey, Vor. X. 
‘ 
Oryzomys minutus (Tomes). Prcmy Oryzomys. 
Two specimens, Mountains northeast of Otuzco, near head of Rio 
Chicama. Altitude 10,000 feet. 
These are practically indistinguishable from specimens from the 
south side of Mt. Pichincha, Ecuador, which may be regarded as prob- 
ably typical of O. minutus. They differ from O. dryas mainly in color, 
being much duller and more grayish above, paler below, and with the 
ears less blackish, and therefore in less contrast with the surrounding 
parts. In cranial characters they are closely related only to O. dryas 
and differ from O. stolezmanni and allies in having more delicately 
formed skulls, with very small teeth, a non-projecting zygomatic plate, 
and a full rounded relatively broad braincase. Whether these char- 
acters can be detected in the immature type of O. minutus will doubtless 
remain uncertain until the type can be carefully compared with an 
ample amount of pertinent material. 
Oryzomys dryas Thomas. 
Nine specimens: Mountains east of Balsas (3), Tambo Almirante, 
near Uchco (1), Tambo Ventija, near Molinopampa (5s). 
These small mice were taken in dense forest where there was great 
humidity but no very high temperature. In the flesh, they present a 
very characteristic appearance, somewhat different from the normal 
““pigmy Oryzomys’’ and resemble rather some of the full-furred Retthro- 
dontomys of southern Mexico and Central America. Their soft woolly 
pelage, richly ochraceous under parts, and sharply contrasted blackish 
ears amply distinguish them without reference to cranial. characters. 
If not identical with typical O. dryas from Ecuador, their departure from 
it can only be very slight since they conform in every respect to the 
original description of the species. 
The resemblance of this diminutive mouse both externally and 
cranially to certain species of Rhipidomys is noteworthy. Its slender 
hind foot and its laterally pitted palate are the only obvious objections 
to stating that it is an exact minature, for example, of R. fulviventer. 
If it had been chosen as the type of Oligoryzomys instead of the typically 
oryzomyine O. navus, some slight grounds might be urged for the 
recognition of such a subgenus. 
Oryzomys laticeps nitidus Thomas. 
Twenty-two specimens: Lagunas (3), Moyobamba (11), Poco Tambo 
(r), Tambo Yaku, near Rioja (6), Yane Yaku, near Yurimaguas (1). 
