130 Mr. 0. Tliomas on 



10. Oryzomys yunganus, sp. n. 



(J. U75. Charuplaya, 1350 ni. 19th June, 1001. 

 A member of tlie 0. laticeps group, most closely allied to 

 O. pereneiisis, All., but more utiitorinly rufous. 



Size about as in other members of the group. Fur close 

 and glossy, about 9 millim. long on tlie back. General colour 

 dark fulvous, finely and profusely lined with black. Head 

 greyer, sides and rump clearer and stronger rufous. Under 

 surface soiled whitish, the bases of the hairs slaty, their tips 

 dull white ; line of demarcation on sides fairly marked. 

 Tip of muzzle whitish, base of whiskers brown, continuous 

 with a dark ring round eyes. Forehead greyish, lined with 

 black. Ears very short-haired, pale brown, not contrasting 

 with the general colour. Hands and feet silvery white above. 

 'J'ail almost naked, very finely scaled, whitish below proxi- 

 mally, the remainder greyish brown. 



Skull, as compared with that of 0. perenensis, shorter, with 

 more expanded zygomata (in the aged type). Interorbital 

 region narrower. Molars shorter, but much worn in the 

 type. 



Dimensions (measured in the flesh) : — 

 Head and body 125 millim.; tail 128; hind foot (s. u.) 28 ; 

 ear 21. 



Skull: greatest length 3 r3 ; basilar length 25 ; zygomatic 

 breadth 16*5 ; length of nasals 12*1 ; interorbital breadth 4*5; 

 palate length 13*7 ; diastema 8"1 ; palatal foramina 5x2*4; 

 length of upper molar series 4'9. 

 Hah. and tyjie as above. 



This species may be distinguished from its other Andean 

 allies by its more fulvous general colour, siiorter molars, and 

 narrower interorbital region. Two specimens closely similar 

 to it were previously obtained by Mr. Simons near Mapiri, 

 further north-west in Bolivia. I confess that I think the 

 various local forms of this intricate and difficult group might 

 be more properly considered as subspecies than species ; but 

 as Dr. Allen has described the oth^r forms as species, it will 

 be less confusing to do the same in the present case. 



11. Oryzomys Slolzmanm, Thos. 



12 (J, 4 ? . Charuplaya. May to July. 



J. Choro, 3500 m. Ilth July. 



1 he Charuplaya specimens vary among themselves to a 

 remarkable PNtent, their backs ranging from grizzled grey to 

 deep rufous and their bellies from white to huffy. The 

 variation in size is also considerable. 



