PLATE CXXXII 



Upper Molar Series of Menodus and Allops 

 One-half natural size. (See p. 523) 



A, Molars referred to Menodus tonus?, Carnegie Mus. 558 or 3068. Ttiis specimen represents a stage between the more primitive 



M. heloceras and the more advanced M. proutii {trigonoceras) . It is considerably larger than M. heloceras; it is smaller and 

 much more primitive than M. proutii (trigonoceras), in the form both of its premolars, which have small postero-internal 

 cusps and rounded internal borders, and of its molars, which are narrower. The dimensions of the teeth approach those which 

 we might expect to find in the upper teeth of M. torvus, a form hitherto known only from the lower jaw. 



B, Upper teeth of Menodus trigonoceras, cotype (Am. Mus. 6356), Horsetail Creek, northeastern Colorado, Chadron formation. The 



drawing shows the alveoli for the vestigial incisors, the conical cingulate canine, the sharp cingula of the premolars and molars , 

 the weU-developed postero-internal cusps of the premolars, joined by narrow ridges to the antero-internal cusps, and the 

 relatively elongate molars — all characteristic of Menodus. 



C, Molars referred to Allops serotinus (Am. Mus. 520), Cheyenne River, S. Dak., Chadron formation. The teeth of Allops differ 



from those of Menodus as follows: One or two upper incisors persist on each side; the canine is flattened anteroposteriorly, 

 the premolars and molars are wider transversely, the postero-internal cusps of the premolars in A. serotinus are less distinct 

 than in Menodus. In all these characters, except the flattening of the canine, Allops resembles Brontops. 



