No. i.] OSTEOLOGY OF PCEBROTHERIUM. 55 



The glenoid cavity is very small, but has a high post-glenoid 

 process, as in the horse. The sphenoid region has the relations 

 general among artiodactyls ; the foramen ovale lies in the ala 

 posteriora, and there is no ali-sphenoid canal. The condyle of 

 the lower jaw is spherical, instead of being transversely extended 

 as in the true ruminants ; the coronoid process is straight and 

 pointed, not curved, and a process for muscular attachment 

 arises from the angnlus mandibulce. 



Of the two genera, Camelus presents the family characteristics 

 in excess, as compared with the llama, which is in so far a less 

 extreme form. In the latter the frontal zone is more extended, 

 and encroaches upon the parietal zone behind the orbits. The 

 orbits are not placed so far forward, and the jugal and lachrymal 

 are more extended upon the face. In front of the jugal there 

 is a considerable vacuity. The premaxillae reach the nasals. 

 The posterior nares are not so high, but extend farther forward 

 than in the camel ; and the spheno-maxillary fossa is, even in 

 old animals, not entirely obliterated. The external supra-orbital 

 openings are opposite the internal ones. 



"AH this probably places the group of the camels outside of 

 any other relations to existing ruminants than those of physi- 

 ognomical similarity, and even the selenodont type of dentition 

 appears to be rather analogical . to than identical with that of 

 the ruminants proper. Among living ungulates no group stands 

 nearer to the camels, with regard to the plan of skull-structure, 

 than that of the perissodactyl horse " (No. 26, p. 19). 



These peculiarities occur in a less marked degree in the 

 skull of Pcebrotlievium. The cranium is shorter, narrower, less 

 capacious and less rounded. The orbits are placed further back 

 even than in the llama, and approach very near together, so that 

 an inter-orbital septum is formed, almost as in the tragulines. 

 They are not so prominent, nor directed so much anteriorly as 

 in the recent forms, and are not quite enclosed by bone ; the 

 Supra-orbital fissure is widely open, though not so deep as in 

 the recent genera. The face is very low, especially in front ; 

 and its upper contour descends regularly from above the orbits 

 to the anterior nares. Owing to the completely brachyodont 

 condition of the upper molars, the alveolus is extremely low, 

 and the orbit is separated from the molars by a very small space. 

 The nasals are extremely long and narrow, and do not show the 



