44 Bulletin American Museum of Natural History. [Vol. XIV, 



little older and a little larger than the other. The smaller has 

 been taken as the type, owing to the poor condition of the skull 

 of the other. The specimens were collected at Inca Mines, Sept. 

 14 and Oct. 9, 1900. 



Rhipidomys ochrogaster is one of the largest species of the 

 genus, exceeded in size apparently by only R. couesi (All. & 

 Chapm.) from Trinidad. All of the other buff-bellied members 

 of the group are very much smaller, and otherwise obviously 

 different. It differs from Hesperomys {Rhipidomys} leucodactylus 

 Tschudi, the only other described Peruvian species, in being more 

 than one third larger, and in its ochraceous instead of whitish 

 (" subtus albescens ") underparts. 



*i4. Phyllotis boliviensis (Waterhouse). Ten specimens, 

 all adult, five of which are from San Antonio, collected Oct. 16, 

 and five from Tirapata. The species was not met with at Inca 

 Mines. 



This species appears to be in part diurnal, as long since ob- 

 served by Bridges (Ann. and Mag. Nat. Hist., XVII, 1846, p. 

 483). Mr. Keays obtained most of his specimens by shooting 

 them while they were feeding on the grass, early in the morning 

 and late in the evening. 



The collector's measurements of these 10 specimens may be 

 summarized as follows : Total length, 185 (177-216) ; head and 

 body, 104 (95-114) ; tail, 82 (76-102) ; hind foot, 24 (23-25). 



* 15. Phyllotis osilse, sp. nov. 



Type, No. 16503, ? ad., Osila, Peru (alt. about 12,000 feet), Oct. 19, 1900 ; 

 coll. H. H. Keays. 



Above fulvous gray, slightly darkened with black-tipped hairs, especially 

 along the middle of the back ; cheeks and sides pale dull fulvous (about ' cream 

 buff' of Ridgway), sharply separated from the white of the ventral surface; 

 sides of nose grayish white ; lower parts white, the hairs plumbeous for the 

 basal two thirds ; pectoral region and median line posteriorly (for a short dis- 

 tance), and also a small area at base of tail, faintly tinged with buff ; ears 

 large, blackish-brown on both surfaces, nearly naked externally, clothed within 

 with short fine dusky hairs ; upper surface of hands yellowish white, of feet 

 clear white ; tail very long, slightly penicillate, dusky on the median line above, 

 sides and below white, the lower surface thickly covered with soft silky white 

 hairs, the upper surface sparingly clothed with dusky hairs, through which the 

 annulations are plainly visible. 



Measurements. Type, total length, 232 mm. ; head and body, 99 ; tail, 133 ; 



