NATURAL SCIENCES OF PHILADELPHIA. 289 



there are others about the eye and ear. The eye is of moderate 

 size, and situated much nearer to the ear than to the nose. The 

 ear shows very conspicuously the prominent lobe of the antitragus 

 which is the chief external peculiarity of this genus as compared, 

 with Gricetodipus ; and opposite to it, on the other side of the 

 notch, there is a similar and smaller but still very evident tubercle, 

 just within the border of the ear. These two prominences together 

 cause the notch of the ear to be very strongly denned, and the 

 margin of the external ear is altogether excluded from the notch. 

 The contour of the ear is broadly rounded. The slit of the cheek 

 pouch is about half an inch long, beginning on the side of the 

 upper lip and curving around with a free border to near the angle 

 of the jaw, there being but narrowly separated from its fellow. 



The details of the palms and soles, as clearly made out from 

 the material before me, are probably applicable also to those other 

 species of the genus of which only dried skins are before me. The 

 palm is entirety naked; it presents posteriorly a pair (inner and 

 outer) of immense smooth tubercles, reminding one of the state of 

 the parts in Geomys. Anterior^ there are three smaller but still 

 very conspicuous bulbs ; one at the base of, respectively, the 2d 

 and 5th digits, and one at the conjoined base of the 3d and* 4th. 

 The palm is otherwise uniformly studded with small elevated 

 granulations, and the digits are similarly roughened underneath. 

 The minute thumb ends club-shaped, bearing upon its back a flat 

 nail, which, like those of the human fingers, does not project at all 

 beyond the end of the digit. The whole thumb is no more con- 

 spicuous than one of the palmar pads. The other digits bear 

 ordinary claws ; the 3d is longest; the 2d and 4th are subequal 

 to each other and but little shorter than the 3d ; the 5th is more 

 abbreviated, but its claw-tip still falls beyond the base of the 4th 

 claw. 



As a consequence perhaps of the desert habitat of this species, 

 the nakedness of the sole, which is one of the secondary characters 

 distinguishing the species of Perognathus from those of Criceto- 

 dipux, is here carried to an extreme. The sole may be called 

 naked without qualification; for the fringe of hairs which droops 

 over its sides does not encroach in the least upon the under surface 

 except just at the side of the contracted posterior part of the heel 

 itself. The whole sole is uniformly paved with minute granula- 

 tions. Among these, one constantly larger than the rest is 



