244 GEOLOGY. 



in this epoch. It will be remembered that the family was first 

 represented in the Eocene of the mountains by the Dawn Horse, 

 or Eohippus, with five toes on the fore feet. The horses abounded 

 all through the Miocene and Pliocene, when in the higher forms 

 in this latter epoch the toes had all, except the middle one, disap- 

 peared, but leaving as a memorial of their former presence the 

 splint bones. It is evident that they must have existed here in 

 Pliocene times in prodigious numbers. In fact, these regions, 

 above any other in any geological age, were dominated by horses. 



One species of Rhinoceros was a contemporary of the Pliocene 

 horses. It was about the size of the Indian Rhinoceros, and its 

 teeth had the same formula. Leidy has named it R. crassus. 



The elephant family (Proboscidians), which first became sharply 

 outlined in the preceding Miocene epoch, was represented in the 

 Nebraska Pliocene by at least two genera and species. Mastodon 

 mirificus (wonderful Mastodon), was first described by Leidy from 

 the Pliocene beds on the Loup. Hayden also found its remains in 

 abundance on the Niobrara. I have also observed them on the 

 Driftwood, and in other localities. The finest molar of this animal 

 that I have seen is in the possession of Captain Palmer, in Platts- 

 mouth, who obtained it from the Republican Valley. It is finely 

 agatized, and is remarkable for its beauty. It is fortunate for us 

 that it fell into the hands of a gentleman who will retain it in the 

 State. This species of Mastodon belongs to Falconer's subgenus 

 Tetralophodon. Leidy was uncertain whether it had tusks. A 

 badly decayed section of a skull which I found on the Driftwood, 

 and which unfortunately fell to pieces in taking it out, had a section of 

 one tusk left. It is my own conviction that it had tusks in both 

 jaws. This species has not yet been found elsewhere outside of 

 Nebraska. 



The remains of a gigantic elephant (Elephas imperator) was also 

 found by Hayden on the Niobrara, and described by Leidy. It 

 was either distinct from the elephant that appeared afterwards dur- 

 ing the Quaternary, or else was of larger size. A portion of the 

 femur of what I take to be this species, now in the cabinet of the 

 University, is certainly more robust in form than that of the 

 Quaternary elephants. The remains of other species have been 

 found on the Niobrara and Loup, but have not yet been specifically 

 described. It is evi lent, therefore, that in Pliocene times elephants 

 and mastodons were abundant over the land surface of Ne- 

 braska. 



