NO. 2333. MAMMALIA COLLECTED IN PERU BY HELLER— THOMAS. 229 



'Skull (pi. 14, fig. 2) about as in 0. dry as, rather more robust than 

 in O. minutus. 



Dimensions of the type : Head and body, 83 ; tail, 134 ; hind foot, 

 22.5 ; ear, 15.5. Skull, greatest length, 23.5 ; condylo-incisive length, 

 21; zygomatic breadth, 13; nasals, 8.2; interorbital breadth, 3.2; 

 breadth of brain case, 11 ; zygomatic plate, 1.8 ; palatilar length, 9.7 ; 

 palatal foramina, 4.2 ; upper molar, series, 3. 



Type. — K^wlt female from Torontoy, U.S.N.M. No. 194795. 

 Orig. No. 255. Collected May 15, 1915. "At timber line." 



Sixteen specimens, as follows: 



Torontoy, 9,500-14,000 feet, 8 (Nos. 194788, 194795, 194866, 194868- 

 71, 195103). 



Machu Picchu, 6,000-12,000 feet, 3 (Nos. 194872-3, 195104). 



Ocobamba Valley, 9,100 feet,- 5 (Nos. 194874-5, 194877-9). 



After reading Mr. Osgood's remarks ^ about O. dry as and reexam- 

 ining our material I came to the conclusion that this group of 

 Oryzomys may very well have a special subgeneric name, and would 

 suggest Microryzomys, with genotype 0. minutus. The non-produc- 

 tion forward to the zygomatic plate and the proportionally small 

 molars would form the chief diagnostic characters, while, as Mr. 

 Osgood says, the general appearance of the species shows something 

 quite special and different from the other members of the large genus 

 Oryzomys. 



Within the group this Peruvian form differs from O. di^as by its 

 duller color, more like that of the Pichincha O. minutus, and from 

 both of those species by its longer ears. 



I may record that an examination of the young type of O. minutus 

 received with the Tomes collection in 1907 (B. M. 7.1.1.112) quite 

 confirms the reference to that species of the Pichincha specimens sent 

 us by Mr. Soderstrom in 1898. Young as it is, it shows the charac- 

 ters of Microi-^jzomys in all respects. 



32. NEACOMYS SPINOSUS Thomas. 



Three specimens from San Miguel, 4,500 feet (Nos. 194838-9, 

 195116). 



Osgood has drawn attention' to the variation from white to buffy 

 in the belly coloration of this species, a variation repeated in a series 

 from the Perene collection of Simons. The present specimens have 

 white bellies, but the hairs in one are white throughout, while in the 

 other they have slaty bases. 



1 Field Mus. Nat. Hist. Publ., Zool., vol. 10, p. 158, 1914. 

 ''Idem. p. 160, 1914. 



