

South Dakota School of Mines 91 



Amynodontidae. 



Poor material, not named specifically. 

 Rhinocerotidae. 



Trigonias osborni Lucas. 



Leptaceratherium trigonodum Osborn and Wortman. 

 Caenopus platycephalus Osborn and Wortman. 

 Caenopus mitis. Cope. 

 ^Middle Oligocene. 

 Hyracodontidae. 



Hyracodon nebrascensis Leidy. 

 Hyracodon major Scott and Osborn. 

 Amynodontidae. 



Metamynodon planifrons Scott and Osborn. 

 Rhinocerotidae. 



Caenopus occidentalis Leidy. 

 Caenopus copei Osborn. 

 Caenopus simplicidens Cope. 



Leptaceratherium trigonodum Osborn and Wortman. 

 ' 'Hyracodon" planiceps Scott and Osborn. 

 L'pper Oligocene. 



Hyracodontidae. 



Poor material, not named specifically. 

 Rhinocerotidae. 



Caenopus tridactylus Osborn. 

 Caenopus platycephalus Osborn and Wortman. 

 Lower Miocene. 



Rhinocerotidae. 



Diceratherium cooki Peterson. 

 Diceratherium niobrarense Peterson. 

 Diceratherium arikarense Barbour. , 

 Diceratherium petersoni Loomis. 

 Diceratherium schiifi Loomis. 

 Diceratherium aberrans Loomis. 

 Aceratherium stigeri Loomis. 

 Aceratherium egrerius Cook. 

 Upper Miocene. 



Aphelops brachyodns Osborn. 



Many references to the literature may be found in the List 



of Fossil Mammals and in the Bibliography given near the close 



of this paper. Among the more comprehensive papers the one 



by Prof. Osborn, treating of the older forms, has been men- 



