Cope.] ^ JO [March 7, 1884. 



Fig. 6. Palatopterygoid and mandibular arches of a fourth individual 

 from right side, with km, hyomandibular. 



Fig. 7. Superior tooth of external row, without apices of two of the 

 cusps ; from the palatine bone of the specimen represented in fig. 5 ; one- 

 half larger than nature, anterior view. 



Fig. 8. Tooth of Didymodus platyptemus Cope, nat. size, from above 

 posteriorly. 



Fig. 9. Tooth of a second specimen of Didymodus platypternus from 

 below. 



Pkinted July 1, 1884. 



