102 ON AN EXTINCT MAMMAL ; 
descending gently from the tips of the nasals towards the 
nasofrontal sutures, then apparently sweeping upwards upon the 
frontals with an open curve. But the whole of the hinder half of 
the cranium is too greatly crushed and distorted to yield reliable 
characters. 
MANpDIBLE.—The lower incisor with a more sudden contraction 
of the upper portion of its inner side than the upper, an actual 
increase in the tumidity of the base on that side being thereby 
brought into greater relief; the directions of curvature as in the 
upper tooth ; the surface of wear much the same in position and 
extent, but having its anterior apical portion more elongate and 
presenting more as a distinct facette, being in one of the teeth 
separated by an unworn tract of enamel from the smoothly worn, 
downwardly sloping, and concave surface of the interoposterior 
apical two-thirds of the tooth ; the tips of the two pairs of incisors 
at exactly the same distance apart. ‘The premolar in general form 
a truncate ellipse, its single cusp occupying its anterior two-thirds, 
its surface of wear an oval tract sloping caudad (and a little 
proximad) towards the base of the lobe, which is limited behind 
by a narrow semicingulum springing from the middle of the base 
on each side; on the inner fore angle a remnant of the indent 
usually representing in this family the forward extension of the 
inner basal ridge. The molars normal in character, profoundly 
degraded by wear, their pre-and postbasal ridges, probably feeble 
in themselves, almost obliterated by fore and aft compression ; the 
last molar #°, only, with its two grinding surfaces still separate, the 
foot of the mid-link remaining intact ; the postbasal ridge of this 
molar very narrow, and connected by a submesial ascending link 
or ridge with the hinder enamel edge of the posterior lobe. The 
molar series as a whole nearly straight on its inner edge, 
moderately convex on its outer, the breadth of the teeth increasing 
slowly from the premolar to the fore lobe of the last molar. On 
the inner side of the crowns of the premolar and anterior molars 
the enamel has disappeared, leaving a smoothly-worn surface which 
in m* is continuous with that of the grinding plane, and in f® is 
excavated from the side of the crown. 
The mandible narrow, its rami converging at a more acute angle 
than is usual in the family ; the intermandibular space subspatulate 
in section, being broader over the symphysis than between the 
anterior molars; the gradient of the symphysis 40°, its infero- 
posterior edge opposite the anterior fang of the premolar; the 
diastemal edge of the mandibular wall rising gently from the 
incisor outlet towards f%, and thinning off rapidly as far as the 
