176 



TTNGFLATA. 



The carpus ia therefore of a more primitive structure than the 

 tarsus. Both the carpal and tarsal bones interlock to a slight 

 extent ; the astragalus is flat ; the feet plantigrade, short, and 

 provided with five digits ; the fibula articulates with the calcaneum. 

 The brain is very small. The cheek- dentition is of a primitive 

 lophodont type, the crowns of all these teeth being very short, and 

 the upper true molars and the hinder premolars bearing two main 

 oblique transverse ridges, which usually form one or two Vs. 

 Upper and lower canines are always present. 



Section CORYPE.ODONTIA. 



This section (Pantodonta of Cope *) is distinguished by the 

 presence of upper incisors, and a third trochanter to the femur ; 

 and the absence of a head to the astragalus. There are no 

 protuberances on the cranium ; and the development of the upper 

 canines is not excessive. 



Family COEYPHODONTID^E. 



The upper premolars are simpler than the true molars, and there 

 are frequently two V's in the latter ; in the lower molars there are 

 two transverse ridges, of which the anterior gives off a process, so as 

 to form a distinct V, with the angle pointing outwards (see 

 woodcut, fig. 26). Numerous genera have been established 2 . 



Fig. 26. 



Coryphodon hamatus, Marsh. The left upper and lower cheek-dentition ; from 

 the Eocene of North America. \. (From Marsh's ' Monograph of the 

 Dinocerata.') 



1 See Proc. Amer. Phil. Soc. Tol. xx. p. 445 (1882). The adopted name was 

 applied by Marsh. 



2 See Amer. Nat. vol. xviii. p. 1194 (1884). 



