g6 Bulletin American Museum of Natural History. [Vol. X, 



present in full in both jaws ; the inferior canine is small and 

 incisiform ; the superior canine is large, with the characteristic 

 D-pattern of the Oreodonts on cross section, and the first inferior 

 premolar is enlarged and caniniform as in the Oreodonts. The 

 first superior premolar is two-rooted with a high, compressed 

 cutting crown, the second is similar but somewhat larger, the third 

 has a principal broad, lunate external cusp and a faint internal 

 cingular ledge. The fourth premolar crown is composed of a 

 single external and internal cusp, much as in the Oreodonts. 



The superior molars closely resemble those of Protoreodon 

 {Eomeryx) in the composition of the crown, so far as can be 

 determined in their advanced stage of wear in the type specimen. 

 It is impossible to say whether or not there were anterior inter- 

 mediate cusps present, but judging from certain appearances in 

 this region of the crown, I am inclined to think that less worn 

 teeth would show them. The mesostyle consists of a vertical 

 pillar as in the Oreodonts generally, and not of a wide open loup 

 as in Agriflchcerus. 



In the lower jaw the incisors and canines are of the typical 

 oreodont pattern, but they are unusually procumbent in position. 

 The first premolar is enlarged and caniniform, the second simple, 

 the third with a small internal cusp and posterior heel, and the 

 fourth similar in pattern, excei)t that the internal cusp is smaller 

 and the heel more pronounced. The lower molars are almost 

 identical in structure with those of the early Oreodonts. 



The whole skull differs from that of the Oreodonts in its more 

 slender proportions. This is particularly noticeable in the lower 

 jaws, which are relatively long and shallow, especially in the 

 region of the symphysis, in marked contrast with the deep and 

 abrupt chin of the Oreodonts in general. There does not appear 

 to have been a preorbital pit present, and the orbit was not 

 enclosed by bone posteriorly. The ])resent genus may be distin- 

 guished from its contemporaries in the following dental characters, 

 viz.: from Proloreodon {Eomeryx) in the possession of diastema 

 in both jaws and the full number of incisors in the upper jaw.' 



' In ;\11 of our material 1 have not yet seen a specimen among the Oreodonts other than 

 Lepioreodon that has a full set of incisors in the upper jaw. Marsh figures the type of 

 Eomeryx piitnilis with but two superior incisors, and \i Protoreodon has the full complement, 

 as believed by Scott, then the two genera are certainly distinct. In two specimens in the 

 Musuem collection which correspond closely with P7-otoriodon parvus, as described by Scott, 

 there is but a single incisor on each side above, and the premaxillae are widely separated from 

 each other in the median line. 



