110 The Badiland Formations of the Black Hills [Region 



Fignre'i6— Restored skeleton of Agriochoerus latifrons. After Wort- 

 man, 1896. 



able in that its toes were apparently armed with claws instead 

 of hoofs and the first toe (the thumb) of the fore ipot seems to 

 have been opposable. Aside from its foot structure the animal 

 was much like the Oreodon. It was approximately three feet 

 long not including the rather long tail. Mesoreodon is likewise 

 remarkable in that the thyroid cartilage of the larynx was 

 ossified much as in the howling monkey and according to Prof. 

 Scott it must have had most unusual powers of voice. 



, Promerycoehoerus, a larger and heavier animal than those 

 of the earlier genera, has been found in considerable numbers 

 in northwestern Nebraska and eastern Wyoming. Plate 48 

 shows the restored skeleton of Promerycochoerus carrikeri. 

 This skeleton is more than five and one-half feet long and 

 evidently indicates a large bodied slow moving animal the habits 

 of which as has been suggested were perhaps somewhat the 

 •same as those of the hippopotamus. Peterson describes the 

 animal briefly as having a massive head, a short, robust neck, 

 •dorsal vertebrae provided with prominent spines, lumbar 

 vertebrae heavy, thoracic cavity capacious, and the feet large. 



The Oreodons are found in the Lower and Middle 

 Oligocene and are particularly common in what is known as 

 the "lower nodular layer'' (red layer) of the Middle Oligocene 

 fifteen or twenty feet above the Titanotherium beds. It is on 

 account of the abundance of these fossils and their early 

 discovery in the Middle Oligocene that this division of the 

 badland formations was by Hayden given the name of Oreodon 

 beds. Leidy tells us that as early as 1869 he had observed 

 fossils of approximately five hundred individuals among the 

 collections sent him for study. Few general badland collections 

 fail to show specimens of these interesting creatures, but most 



