76 



The iminber of teetli in Hyopsodiis appears to be three incisors, a canine, 

 and seven molars to the series on each side of both jaws. 



Neither incisors nor canines are preserved in any of the specimens we 

 have the opportunity of examining. Two lower-jaw specimens retaining 

 portions of the incisive, canine, and premolar alveoli, and the true molars, 

 apparently prove the numl)er of teeth to be as above indicated. 



The canine tooth of Hyopsodus is comparatively of small size, though 

 larger thmi the incisors or the first premolar. It appears to have about the 

 same size in relation with the other teeth as in Aphelotherium anjd Anoplo- 

 therium. 



The premolars successively increase in size from the first to the fourth. 

 The first possesses a single fang ; the others two fixngs. The anterior two 

 premolars are lost from all the specimens under examination. 



The inferior true molars (Figs. 1 to 9, Plate VI) of Hyopsodus have 

 oblong quadrately oval crowns, with the fore and aft diameter exceeding the 

 transverse, which is about equal to the depth. They are inserted in the 

 usual manner in pachyderms by a pair of fangs, the posterior of which in 

 the last tooth is widened backwardly, as is commonly the case in congeneric 

 animals. 



The crowns are composed of four principal lobes, connate at base ; but 

 the crown of the last tooth has an additional or fifth lobe at its back part as 

 well developed as some of the lobes in advance. A rudiment of this fifth 

 lobe is recognized in the other true molars as a small tubercle, occupying a 

 corresponding position. 



The four principal lobes of the crown of the true molars are arranged in 

 pairs not quite transverse, but slightly oblique, so as to appear somewhat 

 alternating. The fifth lobe of the last molar is opposite the interval of the 

 pair of lobes in advance. 



Of the four lobes, the outer are demi-conoidal, and the posterior one is 

 slightly the larger. The inner lobes are simply conical, and the anterior is 

 the larger. The outer lobes in the unworn condition have acute crescentoid 

 summits, or form V-like ridges, with the arms declining from the pointed 

 angle. The inner lobes in the same condition have pointed summits. 



The contiguous horns of the crescentoid summits of the outer lobes join 

 the antero-internal lobe. Tiie anterior horn of the crescentoid summit of the 

 antero-external lobe curves inwardly to the base of the antero-internal lobe. 



