PLATE CLXXl 



Type Jaw of Brontotherium gigas 

 Plate prepared under the direction of Professor Marsh. One-fourth natural size. (See p. 568) 



Yale Mus. 12009, Colorado, Chadron formation. Ai, Outer side view; A2, front view; A3, crown view of dentition. This important 

 genotype, described in June, 1873, together with other jaws and limb bones, formed the material which Marsh used in defining 

 the genus Brontotherium, family Brontotheriidae, and it was also the first representative of the flat-horned species which were 

 later described under the generic name Titanops. 



The skull subsequently named by Marsh Brontotherium ingens does not belong in the same genus with B. gigas and is now referred 

 to Menodus. Generic characters shown in this jaw are the shallow chin, the swollen canines, the lack of external cingula on 

 the premolars. Pi has been shed; the alveoli for incisors 1 and 2 of the left side are visible. The jaw belonged to a somewhat 

 young adult. The measurements do not differ much from those of jaws called Brontotherium hatcheri by Osborn. 



