188 Mr. O. Thomas on new 
Oryzomys nitidus, Thos. 
R. Inambari. Simons. 
The study of a very interesting series obtained by Mr. 
Simons on the Perené has convinced me that the rafous rat 
which in 1884 * I called “ Hesperomys laticeps, var. nitidus,” 
is only an exceptionally rufous form, neither species nor sub- 
species, but merely a variation of that to which I then gave 
the name of //. laticeps. The specimens called nitidus had 
all been in spirit, and this often tends to turn fulvous into 
red, Now the Perené series, all adult, vary from a dark 
smoky Mus musculus-like 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 daticeps, but 
all, whether brown or rufous, must bear the name of nitidus. 
Specimens of this species, generally in the grey phase, 
have been obtained by various collectors all along the Andean 
slopes from Ecuador into Bolivia. 
Oryzomys Keayst, All, 
3, Rio Inambari. 
9, Limbane. 
These specimens differ considerably from each other, but 
only within the limits shown by a series of the closely allied 
O. Childi of Bogoté, where there is much variation in size, 
and the belly may be anything from a sharply detined 
whitish to a rich buffy continuous with the rufous of the 
sides. 
Such variation is very unusual among American Murida, 
and in the face of it I think it by no means impossible that 
O. albigularis, Tomes, O. Childi, Thos., O. meridensis, 
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 obtusirostris, All. 
3 3 Sh 2, Segrario, 13° 30’ S., 70° 5’ W. 
&, Limbane. 
The different forms of the longicaudatus-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, pl. xlii. fig. 1. 
