Rats allied to Oryzomys and Rhipidomys. 195 
1. Rurprpomys, Tschudi. 
Form modified for arboreal life. Tail heavily pencilled. 
Feet broad, the pads broad and low. Claws short, strongly 
curved, their breadth at base equalling or exceeding their 
Jength on their concave edge. Mamme 1—2=6. 
Skull with large rounded brain-case. Interorbital region 
broad and flat, its edges sharpened into ledges more or less 
overhanging the orbits, but without any upwardly projecting 
beading. 
Antero-internal cusp of m’ slightly reduced, but not 
sufficiently so to affect the general oblong shape of the 
tooth. 
Genotype. R. leucodactylus, Tschudi (Hesperomys leuco- 
dactylus, Tsch.). 
Species and subspecies :— 
bovallii, Thos. microtis, Thos. 
caucensis, All. 
cearanus, Thos, 
cocalensis, All. 
couest, All. 
elatturus, Osg. 
eqguatoris, Thos. 
Servidus, Thos. 
Ffulviventer, Thos. 
goodfellowt, Thos. 
latimanus, Tomes. 
lucullus, Thos. 
macrurus, Gerv. 
mastacalis, Lund. 
milleri, All. 
mollissimus, All. 
nitela, Thos, 
ochrogaster, All. 
pictor, Thos. 
quindianus, All. 
scandens, Goldm. 
sclateri, Thos. 
similis, All. 
yuruanus, All, 
venezuele, Thos. 
venustus, ‘Thos. 
2. Tuomasomys, Coues. 
Syn. Erioryzomys, Bangs. 
Form not specially modified. Tail well haired. Feet of 
normal proportions, the pads high, not broadened. Claws 
comparatively jong and slender, not unusually curved. 
Mamme 1—2=6. 
Skull of medium proportions. Interorbital region nar- 
rower than in Rhipidomys, sometimes concave, its edges 
generally rounded, but sometimes, in the larger species, 
raised .and sharpened, but never forming overhanging ledges 
or distinct beading. 
M* of normal oblong shape. 
Genotype. 7. cinereus, Thos. (Hesperomys cinereus, Thos.). 
