U. S. GEOLOGICAL SURVEY 



MONOGRAPH 55 PLATE CLXXXVIII 



SKULL OF MALE BRONTOTHERIUM PLATYCERAS 



One-fifth natural size. (See p. 579, also PI. CLXXXIX.) Skull referred to Brontotherium platyceras (Am. Mus. 1448), Cheyenne 

 River badlands, S. Dak., Chadron formation. This brontothere has the longed recorded horns and the shortest recorded 

 nasals. The horns in size resemble those of B. curtum and are far larger than those of the type of B. platyceras. The width 

 of the zygomata has been increased by vertical crushing, which has also lessened the height of the anterior narial opening 

 and caused the horns to pitch sharply forward. The jaw here show^n (Am. Mus. 1051) may belong to some other species 



