NATURAL SCIENCES OF PHILADELPHIA. 
157 
Upper Miocene bed D is not unfrequently revealed in the channel of the Nio- 
brara, presenting a very irregular outline, showing most conclusively the great 
erosion that must have taken place prior to the deposition of the Pliocene beds. 
It would seem that after the deposition of the materials that entombed the Mio- 
cene fauna, this whole region was eroded so as to present the same rugged 
features as the Bad Lands of White River, and that the Pliocene beds were de- 
posited upon this irregular surface entombing a second fauna, specifically dis- 
tinct from, yet intermediate between that of the Miocene and our present period. 
I have attempted, in the illustrative section* along the Niobrara, to show the ir- 
regular outline of the bed Z>, prior to the deposition of the recent beds. The 
greatest thickness of Pliocene is always found in the valleys of the streams, and 
in consequence of its loose incoherent character is much denuded, forming thf 
principal part of the material of the sand hills. 
Catalogue of all the Fossils hitherto described^ from the Tertiary Formations of White 
and Niobrara Rivers^ with a table shoiving their stratigraphical position. 
RUMINANTIA. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
Obeodon gracilis, Leidy 
Orbodon Cdlbertsoni, Leidy 
Orbodon major, Leidy , 
Agriochcerus major, Leidy 
Agriochcerus antiquus, Leidy 
PoEBROTHBRiuM WiLsoNi, Leidy , 
Leptomeryx Evansi, Leidy 
Lbptauchenia decora, Leidy 
Leptauchenia major, Leidy 
Protomeryx Halli, Leidy 
Merycodus necatus, Leidy 
Megalomeryx niobrahensis, Leidy. 
Merychochcerus proprius, Leidy.... 
Procamelus occidentalis, Leidy 
Procamelus robustus, Leidy. 
Procamelus gracilis, Leidy 
Meryghyus elegans, Leidy...,. 
Merychyus medius, Leidy 
Meryghyus major, Leidy 
Cbrvus Warrbni, Leidy 
MULTUNGULA. 
21. Chceropotamus {Hyopotamus) americanus, Leidy. 
22. Entelodon Mortoni, Leidy.. 
23. Entelodon ingens, Leidy 
24. TiTANOTHBRiUM Prouti, Leidy...... 
26. Paleochosrus probus, Leidy 
27. Leptochojrus spbctabilis, Leidy 
28. Rhinoceros occidentalis, Leidy 
29. Rhinoceros {Hyracodon) nebrascensis, Leidy.. .. 
30. Rhinoceros crassus, Leidy 
31. Mastodon {Tetrnlophodon) merificus, Leidy 
32. Elephas [Euelephas) imperator, Leidy 
Bods i n 
ascending order. 
A B C D E F 
TJi *'^'^f,.fection along the Niobrara river, as well as the more important one througJj xht- 
mack Hills, has been omitted in th.s paper, and will appear in Lt. Warren's forthcomjnf. 
Iteport, ^ 
1^58.] 
