THE TEETH OF ARTIODACTTLE UNGULATA. 333 



on the same type as those of the rhinoceros (page 317), 

 and present the double crescent ; the upper molars are also 

 referable to the same fundamental forms, though the dif- 

 ference is greater. The laminse (transverse ridges) oblique 

 in the rhinoceros, are in anoplotherium still more oblique, so 

 that they become more nearly parallel with the outer wall, 

 and an accessory pillar is developed at the inside of the 

 anterior laminae. 



Not very widely removed from the anoplotherium is the 

 Oreodon, an Ungulate of Eocene age. 



Like a good many tertiary Ungulates (both artiodactyle 

 and perissodactyle) it had the full typical number of teeth, 

 forty -four ; but its interest to the odontologist is enhanced 

 by the Co- existence of strongly marked canines with molars 

 very much like those of ruminants, a group almost always 

 devoid of canines. 



In the upper jaw oreodon had 



.31 43 

 i c pni m 



i.e. the typical number of each kind of teeth. But in the 

 lower jaw the first four teeth are like incisors, and the 

 tooth which is like a canine is not the tooth corresponding 

 to the upper canine, but to the small upper first premolar. 



(*) Upper and lower teeth of Oreodon Culbertsonii after Leidy (Smith- 

 onian Contributions, 1852). 



