110 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
larger. This is particularly noticeable in the ears. ‘The small arvicola-like 
ears of O. /eucogaster are among its striking external features; in ¢orridus, the 
ears are fully as long as in ordinary Hesperomys, measuring nearly three- 
fourths of an inch long by about half an inch wide. The ears are delicately 
pilous, with fluffy tuft at base ; basally, the membrane is flesh-colored, other- 
wise it is dusky, with a delicate silvery margin. The fore feet have the claws 
noticeably smaller than in average /ewcogaster, but this is a very variable fea- 
ture in the latter species. It is probably owing to this shortness of the claws 
that in ¢orridus the hands are only half as long as the soles; in deucogaster, 
they are almost invariably more than this; sometimes upward of two-thirds 
as long. The hind feet are pilous underneath to the toes, showing only four 
tubercles, as in deucogaster, but the hairiness is not so dense. The tail, like 
the ears, is much longer than in deucogaster. In the latter, it ordinarily ranges 
from 14 to 13 of an inch in length, sometimes scarcely exceeding the length 
of the head, and being usually less than twice the hind foot. In ¢orridus, the 
tail is at least half the head and body together, and noticeably more than 
twice as long as the hind foot. These various discrepancies in form are, in 
fact, so prominent that we have been obliged to remodel in some respects 
the diagnosis of the subgenus, as we originally drew it up from consideration 
of deucogaster alone. 
The colors* are highly characteristic. The snowy-white of the whole 
under parts and: feet of deucogaster is replaced by a yellowish-white, or an 
extremely pale buff or fawn. The dark stripe along the top of the tail is 
very narrow, and falls considerably short of the tip, which is wholly whitish. 
The whole muzzle is whitish, as in dewcogaster ; the fluffy hairs about the ears 
give rise to a pale patch in front of each, which, with the dusky body of the 
ear and its silvery edging, produce a parti-coloration not seen in deucogaster. 
The entire upper parts are of a warm though rather light brownish-fulvous, 
entirely different from the gray mouse-brown which Jdewcogaster usually 
exhibits, and, moreover, without appreciable darker dorsal area. The line 
of demarkation along the sides is abrupt, as in dewcogaster. 
The animal is apparently somewhat smaller than an average leucogaster, 
but not much so, and not less than some specimens of the latter. No. 9886 
measures, nose to eye, 0.50; to ear, 0.95; to occiput, 1.25; to root of tail 
“Our type has been skinned out of alcohol; still, we are not sure that the fluid has appreciably 
affected the coloration, for specimens of leucogaster which have lain in spirits a much longer time are not. 
changed perceptibly. 
