ORIGIN, RELATIONSHIPS, AND PHYLOGENY 



27 



this family, which seems to begin with a sudden burst of upper Oligocene to lower Miocene eporeo- 

 donts in California, Oregon, Montana, North and South Dakota, Colorado, Wyoming, and 

 Nebraska, would be more logically explained. 



It is my belief that Merycoidodon will be found in California, and I feel certain that it existed 

 in Oregon and have so identified from that area some maxilla; and rami with teeth in the Marsh 



Limnenetes 

 pla+yceps 



Eporeodon 

 dickinsonensis 



Mesoreodon 

 meqalodon 



Promerycochoerus 

 qrandis 



Merycochderus 

 maqnus 



Pronomo+herium 

 altiramum 



Pm.4 Pm.3 

 Lower 



Pm.4 Pm.3 

 Upper 



Fig. 4. — Third and fourth premolars of Limnenetes, Eforeodon, Mesoreodon, Promerycocko?rus t Merycochcerus, and 



Pronomotherium. (After Loomis, 1924.) 



Collection, though with a query, since the complete skulls are not known. Leidy for a time believed 

 that Merycoidodon existed in Oregon but later wavered on this point. 



It is this trend of thought which makes me so skeptical of the exact position of Eucrotafhus. 

 The crux of the whole matter lies in the recovery of the skeletons of these species assigned to 

 Eforeodon and in the discovery of specimens of Merycoidodon showing the incipient ossification 

 of the inflated bulls. These may be hard to detect, and the basicranial region should be cleaned 

 with the utmost care. It is very probable that the bulls were cartilaginous. If so, they would not 

 be preserved. 



