the crown is compressed, and shows a distinct cutting edge 

 posteriorly. It is short, and tapers rapidly ; in this respect 

 differing from Notharctus, Leidy, which has a long recurved 

 canine. The first and second premolars are inserted each by 

 a single fang ; the third and fourth by two. The third pre- 

 molar consists of a simple conical crown with a small pos- 

 terior heel ; and the fourth has this heel enlarged, with a small 

 tubercle developed inside and slightly behind the principal 

 lobe. All the premolars have striated enamel, and very feebly 

 marked basal ridges. 



The true molars are considerably larger than the pre- 

 molars ; the third is the longest of the series, and the second 

 is the widest. They all seem to be inserted by two fangs. 

 The posterior fang of the last molar is a flat quadrate, of the 

 same size throughout, having a great fore-and-aft diameter, 

 and apparently no nerve cavity. The mandible is strong but 

 shallow, has a curved alveolus and lower margin, and the 

 teeth form a curve Avith convexity outwards. The symphy- 

 sis is short and oblique. 



This genus presents a close resemblance to the modern 

 Lemur, but at the same time shows several differences. We 

 may give these differences in systematic order : (i) Greater 

 number of premolars, in Tomit/icrium = 4, in Lemur = 2. It 

 will be observed, however, that the first and second premolars 

 of Tomitherium are very small and single-rooted, and that 

 their disappearance is a comparatively slight change. (2) The 

 canines are subcircular in section, not nearly so much com- 

 pressed. (3) Greater breadth of the molars in proportion to 

 their length. (4) Two internal cusps on the molar. (5) Much 

 greater size of the last molar. (6) Greater depth and thick- 

 ness of the jaw. (7) Greater curvature of alveolus and 

 lower margin of ramus. (8) Longer and more oblique sym- 

 physis. 



The third and fourth premolars of Tomitherium correspond 

 almost exactly to the first and second of Lemur, but they are 

 not quite so high and sharp. The interior tubercle of the 

 second premolar is not so distinct in the latter genus. 



In the second specimen the cusps are all low, and the 

 crests prominent, giving the molars something of the appear- 

 ance of Opisthotomus. This difference is probably sexual. 



