Peterson : Oste(5logy of Oxydactylus. 441 



pansion of the niaxillaries is more gradual in that genus. In O. 

 /on^i^i/'e-s as well as in other Loup Fork forms the anterior i)art of the 

 maxillary expands rapidly to meet the posterior margin of the pre- 

 maxillary. Thus the facial region is constricted behind the premaxil- 

 laries. Owing to the much more elongated xi\\\zz\& oi Porhrotheriiun 

 the corresponding expansion of the maxiliaries is more gradual in that 

 genus. In O. /oni:^i/>es the palatine plates of the maxiliaries are pro- 

 portionally shallower than they are in the recent forms, and, as in the 

 latter, they extend well in front of the canines. 



The premaxillaries are comparatively heavy especially at the sui)ero- 

 anterior margin, and they are expanded laterally as much as they are 

 in the llama, forming an ovate and oblique narial opening. In 

 Po'cbrotherium the superior portion of the premaxillary is much broader 

 than that of O. iongipes, which again is much broader than in the 

 recent genera. In Poebrotherium the premaxillaries are in contact 

 with the nasals throughout one third the length of the latter, as is the 

 case also in O. Iongipes. In the recent genera there is an anterior 

 process of the maxiliaries, which, together with a shortening of the 

 nasals, has reduced the contact of the latter elements with the pre- 

 maxillaries. The palatine plates and the alveolar border of the pre- 

 maxillaries are heavy to accommodate the superior incisors. The 

 anterior palatine foramen is opposite the third incisor. In a number 

 of different individuals of the family Camelidae, both recent and ex- 

 tinct, which have been examined, the position of the anterior palatine 

 foramen seems to be subject to considerable variation. Sometimes 

 they are anterior to the lateral incisors, again directly opposite, while 

 they will often be found nearly posterior to that tooth. 



The Foramina. — The supra-orbital canal, as in Po'ebrotheriitin, is 

 placed well forward on the frontal and as in the recent camel it is near 

 the median line. In the llama the position of these foramina is more 

 lateral and also more posterior. The infra-orbital foramen is above 

 the anterior part of molar J- practically in the same position as in 

 recent genera, except that in O. Iongipes the foramen is closer to the 

 alveolar border. The lachrymal foramen is single and situated within 

 the orbit as in the llama. The anterior palatine foramen is opposite 

 incisor ^, and the posterior is situated anterior to pm. i. The optic 

 foramen occupies the same relative position as in the llama ; that is, 

 immediately anterior to the large opening formed by the confluent 

 foramen rotundum and lacerum anterius. The foramen ovale, as in 



