PLATE CXXXIII 



Upper Teeth of Menodus and Bkontotherium 

 One-half natural size. (See pp. 523, 554) 



A, Menodus giganteus, neotype (Am. Mus. 505), South Dakota, probably Cheyenne River, Chadron formation. 



B, Brontotherium gigas (Am. Mus. 492), Cheyenne River Badlands, S. Dak., Chadron formation. 

 The chief contrasts shown in these figures are as follows: 



Brontotherium (B) 



Upper incisors 



Canines 



Premolars 



Internal border of p^ 



External V's of fourth premolar 



External cingulum of premolars 



Internal cingulum of premolars 



Protostyles of premolars and molars. 

 Hypocones of m', m^ 



Proportions of molars 



External cingulum of molars 



Internal cingulum of molars 



Vestigial or none 



Long, conic 



Transversely narrower, less molariform, 

 with postero-internal cusps connected 

 with antero-internal cusps by a long, 

 slender bridge. 



Rounded 



Barely suggested 



Very sharp 



Sharp 



Feeble or absent 



Less protuberant internally 



More elongate anteroposteriorly 



Sharply defined 



Delicate, more or less continuous 



Two incisors, large and typically flat 

 topped. 



Short, recurved, swelling, with massive 

 posterior cingulum. 



Very broad, more molariform, postero- 

 internal cusps very large, subcircular, 

 and barely if at all connected with 

 antero-internal cusps. 



Subquadrate. 



Well defined. 



Obsolete. 



Massive or partly confluent with base of 

 crown. 



Very large. 



More protuberant. 



Wider. 



Obsolete. 



Discontinuous — that is, lacking opposite 

 protocones. 



