510 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
The generalities of form of this animal are much the same as those of 
its nearest allies. In relative length, the tail nearly equals that of P. penica/- 
latus, but it is uniformly haired throughout, without indication of crest or 
penicillation. The soles are not so extensively denuded as those of P. penicil- 
latus, owing to encroachment of hairs from the sides; still there is a fairly 
naked strip to the extreme heel The tuberculation of the palms and soles, 
and the proportions of ail the digits, are substantially as in that species. The 
animal is much smaller than any other species of the genus, not much exceed- 
ing a Cricetodipus in size. But the most remarkable character is found in the 
structure of the ear: it is singular how sharply distinguished some species 
of the genus are in this respect. In P. penicidlatus, a sharp teat-like pro- 
jection of the antitragus defines the notch posteriorly, and opposite to if, on 
the other side of the notch, there is a similar but smaller prominence of the 
tragus bounding the notch anteriorly; thus the external edge of the ear itself 
is altogether excluded from the formation of the notch. Now, in P monticola, 
the lobe of the antitragus is a broad, flat, upright flap, both relatively and 
absolutely larger than that of P. peniccdlatus, but there is no corresponding 
lobe of the tragus on the other side of the notch, the front border of the 
notch being formed by the external edge of the ear itself This state of the 
parts ‘Is an approach to the condition seen in Cricetodipus, and is a perfectly 
distinctive mark of P. monticola in its own genus. This important distinction 
escaped the describer of the species; but it should be added that it is only 
fully appreciable upon examination of fresh or alcoholic specimens, and that 
the type of the original description had been mounted when examined. Fur- 
thermore, the ears of P. monticola are smaller than those of P. penicillatus, 
and scarcely more than half the size of those of P. fasciatus. 
Another good character of the species is found in the softness and fine- 
ness of the fur. The pelage is not so stiff and firm as in P. penicillatus even, 
and has nothing of the ‘‘spun-glass” character seen in P. fasciatus, and still 
more noticeable in P. hispidus. 
The coloration of the species is mainly distinctive in the circumstance 
that the dark color of the upper parts descends the fore leg to the wrist, 
whereas on all the other species examined the whole fore leg is white. The 
upper parts are an intimate mixture of tawny and blackish, much as in P. 
fasciatus. There is an evident but not very distinct lateral fulvous stripe. 
The under parts, inthe specimen described (No. 7251), are light yellow, but 
