THEORIES AS TO ORIGIN, ANCESTRY, AND ADAPTIVE RADIATION 



765 



A, PlieTiacodus -wortmani 

 (Phenacodontidae), lower 

 Eocene (Wasatch forma- 

 tion). 



B, Hepiodon calcicitjus (He- 

 laletidae), lower Eocene 

 (Wasatch rormation). 



C, Eohippus sp. (Equidae), 

 lower Eocene (Wasatch 

 formation) . 



D, Systemodon sp. (Tapi- 

 ridae), lower Eocene 

 (Wasatch formation). 



E, Lamhdotlic.rium popoagi- 

 cum (Brontotheriidae), 

 lower Eocene (Wind 

 River formation). 



F, Eotitanops horeoJis (Bron- 

 totheriidae), lower Eocene 

 (Wind Eiver formation). 



G, Helaleles sp. (Helaleti- 

 dae), middle Eocene 

 (Bridger formation). 



H, IsectolopMs sp. (Tapi- 

 ridae). middle Eocene 

 (Bridger formation). 



I, Hyrachyvs sp. (Hyrachyi- 

 nae), middle Eocene 

 (Bridger formation). 



J, Eomoropits amarOTUTn 

 (Chalicotheriidae), upper 

 Eocene of Uinta Basin, 

 Utah. 



K, Lophiodon leptorhynchus 

 (after Deperet) (Lophio- 

 dontidae), upper Eocene 

 of Uinta Basin, Utah. 



L, Triplopus cuUtaUs (Tri- 

 plopodinae), upper Eocene 

 of Uinta Basin, Utah. 



M, Pnloplotherium (Paloplo- 

 theriinae), upper Eocene 

 of Uinta Basin, Utah. 



Figure 694. — Skulls of Eocene titanotheres and other perissodact3-ls and one condj'larth {Phenacodus) 

 Originals or reconstructions in the American Museum of Natural History. Side view. .All figures two-fifths natural size. 



