156 FIELD MUSEUM or NATURAL HISTORY ZOOLOGY, VOL. X. 



of braincase 11.4; post-palatal length 7.1; palatine foramina 4.4 x 1.7; 

 upper toothrow 3.7. 



Remarks. This form has approximately the color of 0. arenalis 

 with the size and cranial characters of 0. stolzmanni. 



Oryzomys arenalis Thomas. DESERT ORYZOMYS. 



Twenty- three specimens: Menocucho (9), Pacasmayo (n), Trujillo 



(3). 



This is one of the smallest known species of Oryzomys. It should be 

 compared with Oryzomys peruvianus (Peale) from Callao when speci- 

 mens of that species are obtained. It was found in relatively moist 

 situations at the edge of small swamps or irrigating ditches. 



Oryzomys andinus sp. nov. 



Type from Hacienda Llagueda, upper Rio Chicama, Peru. Altitude 

 6,000 ft. No. 19430 Field Museum of Natural History. Male adult. 

 Collected March 12, 1912, by W. H. Osgood and M. P. Anderson. 

 Orig. No. 4525. 



Characters. A medium-sized Oryzomys allied to 0. stolzmanni, but 

 having a much larger foot and a very long tail. Coloration of the 

 normal oryzomyine type; upper parts pale ochraceous darkened by 

 numerous fine dusky lines ; a slight ochraceous lateral line ; face and head 

 somewhat grayish; under parts creamy white, sharply differentiated, 

 the hairs with slaty bases; ears thinly haired with ochraceous basally 

 and internally, with brownish distally and externally; feet white; tail 

 thinly clothed with very short hairs, brownish above, whitish below 

 for proximal half, gradually becoming dusky toward the tip. Skull 

 similar in general form to that of 0. stolzmanni but relatively narrower 

 and with smaller teeth and audital bullas; palatine foramina much com- 

 pressed; braincase angled and truncate rather than rounded behind; 

 interorbital region and base of nasals slightly concave between sharply 

 angled edges. 



Measurements. Type: Total length 253; head and body 104; tail 

 149; hind foot 26; ear from notch (dry) 16. Skull of type: Greatest 

 length 26.4; basilar length 20; zygomatic breadth 14; mastoid breadth 

 ii ; interorbital constriction 3.8; nasals 10 x 2.8; palatine foramina 4.8 x 

 1.4; diastema 6.7; width of infraorbital plate 2.6; upper toothrow 3.4. 



Remarks. If, as seems highly probable, specimens from Moyo- 

 bamba and Tambo Almirante represent typical 0. stolzmanni, it is plain 



