PLATE V. 



A. <&> ® 



B 



(^ O 



Rectigradations in the Teeth op Eocene Ungulates. 



A. A primitive Equid, Orohipjytis sp. 



B. A primitive Titiuiotliere, Palmosyops paludosus. 



From specimens in tlie American Museum of Natural History. Internal view 

 of lower teeth. 



The circles mark the cusps whicti appear independently in the different phyla ; 

 they are at first barely visible but increase in size in successive geological levels. 



Top View op Three Skulls op Eocene Titanotheres Illustrating 

 Brachtcephaly, Mesaticephaly, and Dolichocephaly Respect- 

 ively. 



(From specimens in the American Museum of Natural History.) 



A. Palaiosyops major, brachycephalic. 



B. Manteocet as manteocei as, mesaticephalic. 



C. Volichorhinus cornulus, dolichocephalic. 



