S90 RODENTIA 



crossing palm obliquely outward and backward from base of 

 thumb. Hind foot longer and more slender ; proportions of 

 digits as in fore foot, but claws of second and third about three 

 times as long as the othei*s, which are of the usual small size ; 

 in old individuals the second and third claws may be worn down 

 to essentially the same size as the others ; sole naked, finely 

 wrinkled ; three small, ill-defined tubercles at bases of main 

 digits, and a fourth at base of hallux ; a faintly indicated fifth on 

 opposite side of sole from fourth. Tail a mere tubercle barely 

 1 mm. in height. 



Colour. — Back, sides and posterior half of head a light 

 yellowish brown somewhat paler than the ochraceous-buff" of 

 Ridgway, the fur everywhere slate-grey beneath surface ; under- 

 parts and legs slate-grey, the yellowish brown of sides usually 

 extending as an evident wash across middle of body ; face, cheeks 

 and region about mouth silvery drab-grey, the two lines of 

 bristle-like hairs extending back from muzzle whitish in rather 

 marked contrast. 



Skull. — The skull is heavily-built, its surface conspicuously 

 ridged, its general form strongly cuneate whether viewed from 

 above or from the side. Dorsal profile slightly convex from 

 front of nasal to lambdal region, the convexity most marked 

 between orbits, the nasals and upper surface of brain-case often 

 flattened or faintly concave ; occiput very gradually sloping at 

 an angle of about 10°, the length of this sloping portion equal to 

 distance from lambda to posterior extremity of nasals ; ventral 

 profile concave immediately behind incisor, then sloping abruptly 

 downward to front of alveolus, from which point it is essentially 

 horizontal to back of occipital condyle. Brain case broadly ovate 

 in outline when viewed from above, the broad occipital shield 

 causing it to appear almost triangular ; sagittal crest well 

 developed in adult, extending from lambdoid crest to interorbital 

 constriction ; occipital shield extending so far forward that the 

 conspicuous, almost squarely transverse lambdoid crest is con- 

 tinuous at its outer extremity with anterior border of zygomatic 

 root, into basal portion of which the antero-external angle of 

 shield appears to be pressed ; outer border of shield extending as 

 a thin plate from auditory meatus to base of zygoma, and roofing 

 over a pit-like area lying between glenoid surface and neck of 

 bulla ; posterior aspect of brain-case entirely covered by the 

 pentagonal occipital shield, no portion of brain-case or inter- 

 orbital region appearing above its upper margin ; lower border 

 of shield longest, postero-external border shortest, antero-external 

 border intermediate in length ; foramen magnum squarish in 

 outline, its height less than half that of shield ; paroccipital 

 processes distinct but small, not extending to level of lower 

 border of foramen magnum ; condyles projecting noticeably 

 behind all other parts of occiput ; base of brain-case with no 

 specially remarkable features ; width of basioccipital behind 



