PLATE CLXII 



Skulls of Brontotherium leidyi 

 One-fourth natural size. (See p. 559) 



A, Skull R, type (Nat. Mus. 4249), Big Badlands, S. Dak., Chadron formation, level middle A. Figure prepared under the direc- 



tion of Professor Marsh. The nasals are long and tapering, the small horns are flattened posteriorly; the skull top is long, 

 and the zygomata slender. 



B, Referred skull (Carnegie Mus. 93), Hat Creek, Nebr., Chadron formation, level lower A ("15 or 20 feet from bottom of lower 



beds" — J. B. Hatcher). This and the preceding skull show that the Brontotherium phylum was already well differentiated 

 from the other genera at the period when the lower "Titanotherium beds" were laid down. 



