66 FOSSIL MAMMALIA OF THE 



it to rise a little higher than the first and third cusp of the same tooth. In the second 

 molar the apex of the mid cusp is broken off, and in the third molar both this and the 

 hind cusp are wanting. Some traces of sockets are visible anterior to the molar series. 



The impression of the angle and lower margin of the ascending ramus shows them to 

 have been slightly inflected. The ramus has a slight general curve, convex downward, 

 from the hind to the fore part, as in the type Triconodon ferox. The lower border of the 

 mandible is moderately thick and rounded. 



The subject of PL III, fig. 13, nat. size, is the hinder half of a left mandibular ramus, 

 outer side exposed, with the three molars and last premolar. 



The coronoid process is preserved. In its height, breadth, and backward curve it 

 resembles that in PItascoIotherium, which is like that in most zoophagous ]\Iursupials. 

 Unfortunately the lower border of the ascending ramus with the angle is broken off. 

 The transverse rounding of the thick lower border of the preserved part of the horizontal 

 ramus is rather oblique, descending from the outer toward the inner surface. 



In this portion of jaw the mid cusp is entire in the third molar, showing the three 

 cusps to be of equal height. The last premolar (/» 4) is represented by its main cone and 

 small hind basal cusp ; the front one, probably present in the entire tooth, has been 

 broken off. The cone, which constitutes the chief part of the crown of the premolar, is 

 subcompressed, pointed, rising higher than the level of the summits of the cones of the 

 succeeding molars. A fine groove indents the outer side close to the front border of the 

 cone. The first molar, mutilated in the present specimen, shows the same degree of 

 inferiority to the second molar as in the right ramus (fig. 11), where it is entire. 



Although tlie depth of the ramus below the last molar is markedly greater than in 

 fig. 11, the three molars are not larger nor do they occupy a greater longitudinal extent. 

 I conclude, therefore, that the subjects of figs. 12 and 13 exemplify a larger and stronger 

 individual of Triconodon fcrox. 



The fragment of the right mandibular ramus (PI. Ill, fig. 19), with the last molar and a 

 portion of the penultimate molar in sitn, shows well some of the characters of the outer 

 surface of the last molar in Triconodon fcrox. 



The hind lobe oim 3 (fig. 19 a) has a shallow oblique depression, marking off a low 

 basal talou. The outer and fore part of the base of the front lobe is similarly marked by 

 an oblique cleft defining a low cingulum, beginning at the fore part of that lobe. Its 

 non-extension along the base of the tooth to the hind talon shows tlie aspect presented to 

 be the outer one. 



There is a slight vertical notch at the hind part of the last cone of the penultimate 

 molar {m 2), marking off a better developed basal talon than in vi 3. This talon or ridge 

 terminates posteriorly the inner basal cingulum. 



The lobes or cones of the homologous teeth are higher and sharper than in Triconodon 



