Peterson : Osteology of Oxydaciylus. 435 



Generic Characters. 



Dentition. — If C| P^ Mf . 



Teeth bracliyodont, superior incisors little reduced. No reduction in the 

 premolars. The first upper molar narrower than the second, which is 

 the broadest in the molar-premolar series. Third cervical vertebra the 

 lon^:;est in the neck : the sixth zuith undivided inferior lamellcR. Limbs 

 greatly elongated and slender. Trapezium presejit. Metacarpals en- 

 tirely separated. Metatarsals separated with the exception of the palmar 

 processes which are coossified. Phalanges without the plarUar rugosities 

 for pads which are present in the recent camels and llamas. Unguals 

 high, narrow and pointed. 



Specific Characters. 



Cranium comparatively small. Third superior incisor as large as the 

 canine. The first superior premolar two-rooted. Molars long and 

 narrow. A short diastetna between the third inferior ificisor and the 

 canine. The fifth metatarsal present and articulating proximally with 

 the fourth by a distinct facet. Distally it is coossified with the fourth. 

 The axis micch shorter than the third cervical. 



Superior Dentition. — In the type specimen (No. 918) (PI. IV, 

 Figs. I, 2 and 3), the first and second incisors have dropped out, but 

 the alveoles are open ; they are each separated by a short diastema. 

 A specimen (No. 667) in the collection, which is referred to the same 

 species as the type, has the incisor teeth in position. These present 

 characters similar to those of Pocbrotherium. They are small, sub- 

 cylindrical in cross-section, with slightly expanded crowns covered 

 by enamel. They show distinct wear in old individuals. This third 

 incisor is present in the type and is a large caniniform tooth equaling 

 the canine in size and similar to it in character. There is a long 

 diastema between the third incisor and the canine ; the latter, is situ- 

 ated just back of the maxillo-j)remaxillary suture and is a strong and 

 slightly recurved tooth. The first premolar is separated by long 

 diastemata from the canine and the second premolar. It is more ob- 

 tuse in the present genus than in Pocbrotherium. Its greatest diameter 

 is antero-posterior, and it is two-rooted. The second premolar is but 

 little reduced and is very similar to that of Po'ebrotherium. The 

 median cusp is closely fused with the anterior and posterior cusps 

 forming a sharp antero-posterior ridge of which the median cusp forms 

 the summit. The second premolar is slightly shorter antero-posteriorly 



