a. S. GEOLOGICAL SURVEY 



MONOGRAPH 55 PLATE CLXXII 



JAWS OF TWO SPECIES OF BRONTOTHERIUM 



le-fourth natural siie. (See pp. 565, 573.) A, Jaw referred to BrontotHeriutn hatcheri? (Am. Mus. 1070), Hat Creek badlands, Nebr., Chadron forma- 

 tion. This ja^v belongs with the skull shown in Plate CLXIX. In the measurements of the teeth this specimen is a little larger than the type of 

 B. gigas. The latter, how^ever, is curved upward in front and does not projedt poileriorly. B, Jaw referred to Brontothsrium medium? (Am. 

 Mus. 1051), Cheyenne River badlands, S. Dak., Chadron formation. This huge jaw^ represents one of the largest knovi^n titanotheres. Its meas- 

 urements are given on page 569. It differs from other known brontotheres in having an angulate chin and in the large size of the teeth 



