188 Mr. 0. Thomas on new 



Oryzomys nitidusj Tlios. 



R. Iiiambari. Simons. 



The study of a very interestuig series obtained by Mr. 

 Simons on the Peren(5 has convinced me that the rufous rat 

 which in ISS-i * I called " Ilespero/nys laticeps, var. nitidas,^ 

 is only an exceptionally rufous form, neither species nor sub- 

 species, but merely a variation of that to which I tlien gave 

 the name of //. /a^/ce/?s. The specimens called nitidaa had 

 all been in spirit, and this often tends to turn fulvous into 

 red. Now the Perend series, all adult, vary from a dark 

 smoky Mus viusculus-Wko, grey to a rich fulvous, at least 

 along the flanks, the dorsal area being still dark. The fulvous 

 specimens tend to have lighter tails below than the grey 

 ones, but the two forms intergrade completely. No doubt 

 the Andean rats will prove distinct from the true laticeps, but 

 all, whether brown or rufous, must bear the name of nitidus. 



Specimens of this species, generally in the gvey phase, 

 have been obtained by various collectors all along the Andean 

 slopes from Ecuador into Bolivia. 



Oryzomys Keaysi, All. 



cJ, Rio Inambari. 

 ? , Limbane. 



These specimens differ considerably from each other, but 

 only within the limits shown by a series of the closely allied 

 0. Childi oi Bogota, where there is much variation in size, 

 and the belly may be anything from a sharply defined 

 v/hitish to a rich bufFy continuous Avith the rufous of the 

 sides. 



Such variation is very unusual among American Muridge, 

 and in the face of it 1 think it by no means impossible that 

 0. albigularis, Tomes, 0. Childi, Thos., 0. meridensisy 

 Thos., and the present animal, which are undoubtedly all very 

 closely allied to each other, may hereafter have to be amal- 

 gamated. Probably I should not myself have given a special 

 name to the Inambari form. 



Oryzomys ohtusirostris, All, 



(? c? (? ? , Segrario, 13° 30' S., 70° -V W. 

 (J, Limbane. 



The different forms of the lonqlcaudatus-Stolzmanni group 

 are exceedingly difficult to differentiate, but I use the name 

 Dr. Allen has applied to the Inambari race. 



* P. Z. S. 1884, p. 452, pi. xlii. fig. 1. 



