6 



INTROD UCTOR Y. 



ing an aberrant group which became extinct long before the close of the Ter- 

 tiary. The indirect relations of these genera with the elephant tribe were 

 apparent from the first, but there is no foundation for a belief that they came in 

 the line of forms ancestral to the Proboscidia. 



The Stratigraphical Report by J. B. McMaster, leader of the expedition of 

 1878, made from his notes and sections of the strata of the Bridger beds as ex- 

 posed in the Washakie basin, points chiefly to the present condition of the strata 

 as they are left by erosion and denudation. As it indicates the level at which 

 the fossils described in the text were discovered, and embraces an outline of 

 the principal topographical features of the country it is published in connection 

 with this memoir. 



The thanks of the writer are gladly expressed to Dr. Arnold Guyot, 

 Director of the Museum, for frequent advice and encouragement, and to Dr. 

 William B. Scott for several suggestions of value. Dr. Franklin C. Hill also 

 rendered much kind assistance in the Museum, 



H. F. O. 



Princeton, July 1881. 



