MAMMALIA. 47 



mirabile from the Bridger Formation of Wyoming, presented Case U. 

 by Professor 0. C. Marsh, is mounted in a special Case 

 marked U. A plaster cast of a skull of Tinoceras ingens 

 (Fig. 37) is placed beneath it ; and a series of brain-casts 

 to show the relatively small size of its brain is arranged in 

 front. The skull bears three pairs of bony prominences, 

 which increase in size backwards, and seem to have been 



Fig. 38.— Skull and lower jaw of Arsinoitlierium zitteli, from the Upper 

 Eocene of the Fayum, Egypt ; one-twelfth nat. size. (Case S.) 



covered merely with skin. These bony horns and the brain- 

 case are almost solid, with very few cavities. The upper 

 canine teeth are much enlarged, and are protected by long 

 flanges depending from the mandible. 



Sub-order 5. — Barypoda. 



Arsinoitherium, from the Upper Eocene of the Fayum, ^^^l-case 

 Egypt, lias a relatively larger brain than the Amblypoda, Case S. 



