440 Annals of the Carnegie Museum. 



oblique to the long axis of the cranium and they do not crowd the 

 basi -sphenoid as in PoehrotJieriiim. The buUje are separated from the 

 paroccipital processes by a heavy, rounded ridge extending as low 

 down as the rest of this entire region with the exception of the par- 

 occipital processes. The pit for the stylo-hyal is comparatively smaller 

 than in the recent genera, and, like that of the llama, is deep and dis- 

 tinctly separated from the styloid groove. On the anterior apex of the 

 bulla there is a sharp conical process somewhat similar to that seen in 

 the camel. The external auditory meatus is as large as that of the 

 llama and has nearly the same relative position. The tympanic region 

 in O. lojigipes resembles that of the llama more clearly than that of 

 the recent camel. 



The pterygoids are comparatively narrow and are not expanded 

 posteriorly as in the recent forms, especially the llama, but the hamu- 

 lar processes are nearly as well developed as in the Tylopoda in 

 general. 



The anterior extent of the palatines can not be ascertained in the 

 type specimen. The pterygoids are moderately long and heavier than 

 in the llama, ending in the hamular processes already mentioned. The 

 posterior nares are long and narrow with the anterior border V-shaped 

 and extending as far as the posterior border of the third molar. The 

 palatine fissure between the posterior apex of the alveolar border of 

 the maxillary and the pterygoids is very shallow. In the llama the 

 posterior nares, the palatine foramen and the palatine fissure are sub- 

 ject to so much individual variation in position, and in some instances 

 also in shape, that they are of little value for purposes of classification. 

 Posteriorly the delicate vomer is broken away in all the specimens at 

 hand, but the rapidly tapering presphenoid would indicate that the 

 vomer has a posterior extension similar to that of the recent forms. 



As in Pocbrotheriiiin and Protomeryx the maxillaries are long and 

 low. In front of the jugo-maxillary suture there begins a long heavy 

 ridge which extends well in front of the deep depression on the upper 

 part of the maxillary situated above premolars ^ and ^. This ridge is 

 entirely obsolete in the recent forms and in these this surface presents 

 a more regularly rounded appearance. In O. longipes as well as in 

 other Loup Fork forms the anterior part of the maxillary expands 

 rapidly to meet the posterior margin of the premaxillary. Thus the 

 facial region is constricted behind the premaxillaries. Owing to the 

 much more elongated muzzle of Poebrotheriiun the corresponding ex- 



