[poz.] 



Osborn, Oli^ocene Titanotheres. 



107 



WM0 



the persistence of the large pair of upper incisors in all the 

 male specimens thus far observed. Certain females appar- 

 ently lack incisors. 

 The horns are very ^- — -^—S-^ 

 long ; the nasals '•■•l^il 



gradually disappear. 



B. bucco Cope. — 

 In the writer's first 

 review the type of 

 this species was con- 

 fused with the types 

 of Syinborodon torvits. 

 It is actually repre- 

 sented by the poste- 

 rior portion of a 

 cranium in the 

 American Museum 

 (No. 6346). The buc- 

 cal section of the 

 zygomata is more 

 convex than in the 

 succeeding species. 



B. gigas Marsh. 

 (Syn., Titanops elatus 

 Marsh). — This is now 



one of the best-known species, including the type in the 

 Yale Museum, and numerous specimens in the American and 

 National Museums previously referred to B. elaUim. 



Smaller and somewhat more primitive varieties of B. gigas 

 are recorded by Hatcher from the Upper Levels of the Middle 

 Beds. 



B. dolichoceras Scott & Osboni. (Syn., Titanops medius 

 Marsh). — Represented by types in the Harvard and National 

 Museums. This species is intermediate in many characters 

 between B. gigas and B. curtuni. 



B. curtum Marsh. (Syn., Menodus peltoceras Cope). — 

 The type in the Yale Museum is supplemented by the 

 female horns named by Cope Menodus peltoceras, also by 



'^/7/ 



'^ 



W'^' 



o 



Fig. 12. Sections of nasals, horns, occiput, zygomata. 

 A, Broniotherium letdyi, type. B, Brontotherium 

 hypocerasy cotype. 



