38 - OREODON. 



rior to the lower canine, a hiatus of sufficient size to accommodate the cusp of the 

 upper one. This hiatus is in a trifling degree less than that posterior to the upper 

 canine. 



The iufeiior incisors are oblique in their position, but relatively, less so even than 

 in the Musks ; and they form a longer arc of a lesser circle than those of the upper 



jaw- 

 When the jaws are closed, the inferior molars are situated within the line of the 



outer lobes of the upper true molars, but anteriorly they are placed very little within 



the outer faces of the upper premolars. 



The intervals between the pyramidal crowns of the premolars are triangular, 

 and the three inferior crowns are included by the four superior ones. 



The crown of the superior canine is directed downward and outward, and, as 

 in the genus Palaiotlierium, it is placed in advance of the canine below; a position 

 which is exceedingly anomalous. Its point projects considerably exterior to the 

 inferior canine, and only its internal angular margin occupies the hiatus in advance 

 of the latter tooth. 



The crown of the lower canine is directed upward, and a little forward and 

 outward; and its point, though projecting slightly exterior to the hiatus provided 

 for it above, is yet within the line of the outer surface of the upper canine. 



The inferior incisors, laterally, are included within the circle of the superior; 

 while the cutting edges of those anterior come in contact with, the edges of the 

 corresponding teeth above. The outer sides of the upper incisors are vertical, and 

 those of the lower incisors incline to, them at an angle of about 50°. 



Superior Molars.— {V\. II. Figs. 1, 3 ; III. 1, 2 ; IV. 6 ; V. 2, 3 ; VI. 2, 3, 4, 6.) The 

 crowns of the upper true molars are composed of four symmetrical lobes, as in all 

 existing ruminants. Among these, they approach most in their form the crowns 

 of the corresponding teeth of the Deer, but they are more expanded trans- 

 versely, and more square, the interlobular depressions more shallow, and the 

 inner lobes are uncomplicated with accessory folds or lobes. Among the extinct 

 ruminants of which we have any knowledge, they resemble most those of 

 Meri/copoiamus ; but they diifer from the teeth of this genus in a number of par- 

 ticulars, more especially in the non-isolation of the outer lobes (which conjoin 

 in a prominent buttress, as in Anthracotherium), and in the relatively slight degree of 

 development of the basal ridge, which does not traverse the bottom of the trans- 

 verse interlobular space, as it does in the Merycopotamus. From the corresponding 

 teeth of Anthracotherium, Hyopotamus, and Caenoiherium, they differ most in the 

 absence of the fifth constituent lobe, which in the former two genera is introduced 

 between the anterior pair of normal lobes, and in the last genus between the poste- 

 rior pair. From those of Dichodon, they differ in the absence of the curiously 

 cuspidate basal ridge, and in the less acuteness of the lobes. Finally, from the true 

 molars of the most aberrant forms of extinct ruminants, the Anoplotherium and 

 Ghalicothermm, they differ as characteristically as do those of any of the existing 

 memljcrs of the family. 



When unworn, the lobes of the true molars have acute crescentic summits 

 elevated to a middle point. The outer lol^es anteriorly, and consequently 



