PLATE IV. 



7, Mammoth. 



Pleistocene. 



Three species, the Colum- 

 bian, Imperial, and Primi- 

 tive are abundant in Ne- 

 braska. 



6, Mastodon. 

 Mastodon anicricaniis. 

 Common in Nebraska. 

 Pleistocene. 



5, Eitbelodon iiiorrilli. 



A trilophodont mastodon 



Pliocene. 



Devil's Gulch, Nebraska. 



4, Tctmbelodon zvillisfoui. 

 A late four-tusker. 

 A trilophodont mastodon. 

 Pliocene of Nebraska. 



3, Tctrabdodoii. 

 An early four-tusked 

 mastodon. 

 Miocene. 



2, Pa/acoiiiasfodnii. 

 Lower Oligocene, Egypt. 



I, Moerithcriuui. 

 Ancestral proboscidean. 

 Upper Eocene, Egypt. 



Plate I 

 Evolution of the Proboscidea. Freehand sketches, approximately to 

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

 Morrill, State Museum. 



