INTRODUCTION. 3 



The remarkable Eocene basin North of the Uinta Mountains, where 

 alone the Binocerata had been found, offered so inviting a field for 

 exploration, that in the spring of the following year, 1871, the author 

 began its systematic investigation. An expedition was again organized, 

 with an escort of United States soldiers, and the work continued during 

 the entire season. Among the very large collections thus secured, were 

 numerous specimens of the D'moccrata, which furnished important 

 characters of the group. 



P7y— Ts^ 



=f:: t^^^h: 





O { §?"" I 



' ' • ' /' r , 



Map siiowino region of Dinoceras beds. 



In the succeeding spring, 1872, the explorations in this region were 

 continued, and soon resulted in the discovery of the type specimen, 

 including the skull and a lai'ge porti(tn cif the skeleton, of Dinoceras 

 nilrabi'Ie, and on tliis new genus the author based the order Binocerata 



