350 Mr. 0. Thomas on some 



Skull: greatest length 36, basal length 30*6, basilar length 

 28*7, greatest breadth 18"5; length of nasals 14 7; inter- 

 orbital breadth 5*2 ; interparietal, length 36, breadth 12 ; 

 palate length to henselion 15*5 ; palatal foramina 7 ; diastema 

 10'6 ; length of upper molar series 4-9. Lower jaw: condyle 

 to incisor-tip 23'6 ; coronoid to angle 10 ; height of ramus 

 below ^n 4*3. 



A second specimen is contained in the collection (an imma- 

 ture female) , which I have little hesitation in referring to the 

 same species. 



Hob. Valley of Vitoc, East Central Peru. Coll. J. Kali- 

 nowski. 



Type: B.M. 94.10.1.2. 



As in the case of "Hesperomys cinereus " *, to which they 

 are undoubtedly nearly allied, I have had great difficulty in 

 assigning this and the next species to their proper genus, as, 

 although Dr. Coues f has attempted to cut the knot by forming 

 for H. cinereus a special group, I do not feel satisfied that it 

 is one worthy of retention. Although the addition of the 

 two species now described to the group would seem to support 

 its position as a separate genus or subgenus, yet there seems 

 to be such a gradation from cinereus through Kalinoioskii, 

 alhiyularis, and meridensis into typical Oryzomys, that I 

 think it better for the present to use the latter name for 

 them all. 



Oryzomys incanus, sp. n. 

 Similar to O. Kalinoivskii in all essential respects, in 

 colour, proportions, and general skull-characters, but distin- 

 guished by its conspicuously smaller size, slenderer muzzle, 

 broader interorbital space, much smaller teeth, and also by 

 the disproportionate slenderness and delicacy of the lower jaw. 

 Dimensions of a male preserved in spirit : — 

 Head and body 104 millim. ; tail 115; hind foot 25; ear 

 17 X 14 ; forearm and hand 29*5 ; heel to front of last foot- 

 pad 10-7. 



Skull : greatest length 30'7, basal length 25, basilar length 

 23, greatest breadth 14*7 ; length of nasals 12'6 ; inter- 

 orbital breadth 5*2 ; interparietal, length 3, breadth 9'2 ; 

 palate length to henselion 12*1 ; palatal foramina 6'1 ; 

 diastema 8*3 ; length of upper molar series 4 - 4. Lower jaw : 

 condyle to incisor-tip 1 9 ; coronoid to angle 7 ; height of 

 ramus below ^n 2*7. 



Hab. Valley of Vitoc, Central Peru. Coll. J. Kalinowski. 

 Type : B.M. 94.10.1.4. 



* P. Z. S. 1882, p. 108. 



t Am. N.at. xviii. p. 1275 (1884). 



