260 TJmversity of Calif ornia Puhlications in Zoology [Vol. 21 



Color. — Mass effect of dorsal area ranging- from dull Front's 

 brown to dark bister, with varying snffnsion or admixture of long- 

 black overhairs, and heavily tipped with warm buff on cheeks, neck, 

 and along the sides. In fresh pelage : hairs of upperparts slate color 

 basally, with light-tipped portion grading from cinnamon buff to snuff' 

 brown, the long overhairs varying from aniline black to blackish 

 brown. Sides lighter than upperparts, decidedly more buffy, with 

 light tipped portions of hairs approaching pinkish buff. Rump darker 

 than rest of upperparts because of predominance of blackish over- 

 hairs. Underparts varying from white to pallid neutral gray, irregu- 

 larly darkened by the slate-colored basal underfur showing through. 

 Inguinal region occasionally washed with buffy ; anal area pure white; 

 Terminal portion of whiskers whitish with blackish bases. Hairs of 

 upper and lower lips whitish. Nose usually lighter than area in front 

 of eyes. Ears large, not concealed bj^ fur, the anterior border furred 

 with hairs the same color as light-tipped hairs of sides. Tail distinctly 

 bicolor, dark blackish brown above and pallid neutral gray below. 

 Hands and feet covered with hairs varying from mouse gray to pallid 

 neutral gray. In worn pelage : much duller, lighter, with grayish 

 overcast in region of shoulders, and with a diminution of the long 

 dark overhairs. In some specimens the long dark overhairs are so 

 plentiful as to conceal the lighter hairs, giving the individual a grayish 

 appearance. 



Skull. — The skull of ))iontanus is relatively large and massive, 

 though slightly smaller than ijosoiiite, becoming more ridged and 

 angular in fully adult individuals. Dorsal profile, with exception of 

 interorbital region, is uniforml}^ convex. Brain case rather deep. 

 Occiput rounded off behind, not obliquely truncate, concealing occipi- 

 tal condyles for the most part when skull is viewed from above. 



Normally with considerable variation in contour of brain case due 

 to differences in age. In sexually adult individuals, the skull is rather 

 long, generally smooth, rounded at sides, convex superiorly, and 

 slightly truncated anteriority by postorbital tuberosities. In fully 

 adult or very old individuals the brain case is subrectangular, flattened 

 superiorly, but not abruptly truncated anteriorly by the postorbital 

 tuberosities, which spread out laterally. Interorbital constriction nar- 

 rower than anterior portion of rostrum. Interorbital ridges distinct, 

 rather closely approaching each other, usually coalescing and extend- 

 ing back to parietals, where in very old individuals they unite with 

 longitudinal ridges. Interparietal strap-shaped, its greatest antero- 

 posterior diameter, exclusive of median projection equaling one-third 

 or more of greatest transverse diameter, and its lateral extremities 

 abruptly truncated. Frontals variable posteriorly, either truncate or 

 emarginate. 



Rostrum long, slender, gradually tapering anteriorly, the least 

 dept'^ behind incisors somewhat greater than width in same region. 

 Posterior terminations of nasals variable, in some straight and in 

 others attenuate, rounded or slightly emarginate, exceeded by nasal 

 branch of premaxillae. Nasals at their widest region in front are 

 conspicuously narrower than rostrum, abruptly constricted anterior 

 to middle, and ma.y extend as far as, but not beyond, plane of incisors. 

 Anterior narial opening normally with vertical diameter greater than 

 transverse. Anteorbital foramen wide and rather high, with superior 



