i6 Envin H. Barbour 



15. Metoreodon 

 Merycodonts 



16. Merycodus necatiis 

 Rhinoceros 



17. Teleoceras 



18. Rhinoceros, undetermined 

 Equids 



19. Parahipptis 



20. Hypohippus 



21. Merychippus 



22. Protohippus 

 2^. Pliohippus 



24. Hipparion 

 Proboscideans 



25. Tetrabelodon zmllistoni, sp. nov. 



26. Mastodon euhypodon? 



27. Mastodon, undetermined 



28. Mastodon morrilli, sp. nov. 



The University of Nebraska, 

 December, 1913 



Plate IV 



Evolution of the Proboscidea. Freehand sketches, approximately to 

 scale, from casts and specimens in the collection of Honorable Charles H. 

 Morrill, State Museum, i, Moeritherium. Ancestral proboscidean, Up- 

 per Eocene, Egypt. 2, Palacomastodon. Lower Oligocene, Egypt. 3, Tetra- 

 belodon. An early four-tusked mastodon. Miocene. 4, Tetrabelodon wil- 

 listoni. A late four-tusker. A trilophodont mastodon. Pliocene of Ne- 

 braska. 5, Euhelodon morrilli. A trilophodont mastodon. Pliocene. 

 Devil's Gulch, Nebraska. 6, Mastodon. Mastodon americanus. Com- 

 mon in Nebraska. Pleistocene. 7, Mammoth. Elephas primigenius. 

 Pleistocene. Three species, the Columbian, Imperial and Primitive, are 

 abundant in Nebraska. Pleistocene. 



Plate I 

 General View of Devil's Gulch. Looking up the canyon. Quarry No. 

 I is at a. 



Plate II 

 Nearing the Brink of the Canyon. Dragging out, by means of block 

 and tackle, a slab containing the skull of Tetrabelodon ■wilUstoni. Quarry 

 No. 2 is at 0. 



200 



