floor of the large orbit. The mandible is slender and com- 

 pressed, with a large dental canal. 



The atlas is small, and has narrow transverse processes, 

 which are perforated by a large vertebraterial canal. The 

 dorsals have considerably depressed centra, and the ribs are 

 slender. 



Measu rements. 



M. 



Length of last molar -025 



Breadth of last molar -030 



Length of second molar -024 



Width of second molar -0305 



Length of last (?) premolar -018 



Width of last premolar -0245 



Length of second lower molar 025 



Width of second lower molar -018 



From Henry's Fork Divide. 



HYRACHYUS INTERMEDIUS, sp. nov. 



Established on the upper true molar series of the righc 

 side. 



This species is intermediate in size between H. agrariut 

 and H. modestus. As in the latter species, the basal ridge ex . 

 tends around the entire crown of the tooth, with a small in . 

 terruption on the antero-external lobe. It is more pronounced 

 in front and less behind than in H. imperialis. The anterio 

 conical buttress is not nearly so well developed as in H. impe 

 rialis ; the valleys are wide, and the descending fold from 

 the antero-external lobe is obscure, scarcely marked at all ii < 

 the first. The transverse crests are strongly arched forwards . 

 and the anterior is very much the longer. The peculiar fea , 

 ture of the species is the position of the postero-externa . 

 lobe, which is pushed to the posterior aspect of the tooth , 

 this is carried so far in the last molar that the two externa , 

 lobes stand on nearly the same transverse line. The anterc . 

 external lobe is much the highest point in the tooth, and v\ 

 the first molar is remarkably sharp. The enamel is consider . 

 ably wrinkled, but not nearly so much as in H. mod^stus. 



