PLATE CLIX 



Jaws of Megacerops riggsi and of Menodus torvus 

 Plate prepared under the direction of Professor Cope. One-third natural size. (See pp. 527, 550, also PI. CLVIII) 



A, Lower jaw of Megacerops riggsi, type (Am. Mus. 6364), Horsetail Creek, northeastern Colorado, Chadron formation. This 



shows the extremely short thick rami and short symphysis. 



B, Unidentified jaw fragment from Colorado, referred by Cope to "Menodus prouiii," which suggests that he intended to include 



under that term titanotheres with two incisors on each side. 



C, Lower jaw of Menodus {"Symborodon") torvus, type (Am. Mus. 6365), Horsetail Creek, northeastern Colorado, Chadron forma- 



tion. This jaw, the genotype of Symborodon, shows the long, slender rami and long symphyseal region characteristic of 

 Menodus jaws. 



