PLATE LXXXVII 



Skulls of Brontops brachycephalus 

 One-fourth natural size. (See pp. 484, 485, also PL LXXXIII) 



A, Paratype (Nat. Mus. 4947), skull B, female, Big Badlands, S. Dak., "west side of Quinn Draw, near the Cheyenne River" 



(J. B. Hatcher); Titanotherium zone (=Chadron formation), lowest levels (14.4 feet above Pierre shale). As compared with 

 the type male skuU (B) this aged female is smaller, more elongate, and slenderer, with small canines and unexpanded zygomata. 

 The much worn molar teeth appear somewhat more primitive than those of the type, especially m'. 



B, Type (Nat. Mus. 4261), skull c, male, Big Badlands (probably Corral Draw), S. Dak., near base of lower Titanotherium zone. 



Generic affinity with Brontops robustus is indicated by the presence of one or two round-topped incisors on each side (the inner 

 pair often drop out in adults) , the stout canines, the retarded postero-internal cusps on p<, the general brachycephalic form of 

 the skull, and the character of the horns. 



