METALOPHODON. 555 



The existence of the posterior transverse crest on the second true molar 

 constitutes a point of nearer resemblance to the Eobasileidoe than is found 

 in the other known Coryphodontidce. 



Metalophodon armatus Cope. 



Proceed. Ainer. Philos. Soc, IriTi, p. 54-3. Annual Report U. S. Geol. Surv. Terrs., 1872 (1873), p. 589. 



Plate xlix, tigs. 1-7. 



This, the only known species of the genus, was found by myself near 

 Black Butte, Wyoming, in the Wasatch formation. The typical specimen 

 consists of a number of teeth of both jaws which I took from two decayed 

 skulls which were partly exposed in a bank of argillaceous material. These 

 skulls were lying close together,, and belonged to an adult and young ani- 

 mal, respectively, as indicated by the relative wear of the teeth. The adult 

 series consists of three incisors, two superior premolars, and three superior 

 true molars, with three inferior premolars. The young animal is repre- 

 sented by one incisor, the superior and inferior canines, three superior pre- 

 molars, and two superior true molars ; also by one inferior premolar and 

 one inferior true molar. The second true molar of the younger specimen 

 is unfortunately wanting, so that it cannot be demonstrated that it belongs 

 to this species, but the other teeth, especially the first and third true molars, 

 correspond so closely as to induce me to suspect that the two animals were 

 members of the same species, and probably of the same herd. 



I first describe the teeth of the adult : 



The incisors are well developed, those of the premaxillary subequal in 

 size. The crown has a convex cutting edge and flat inner face. The outer 

 face is convex. In some the inner face is more concave, and is bounded 

 by a weak cingulum next the root. 



The superior premolars present a single external crescent of acuminate 

 outline, and a smaller, more transverse one, within. A cingulum bounds 

 the crown fore and aft, but is wanting at both external and internal bases 

 of the crown. The posterior sends a branch to the apex of the internal 

 lobe. In the fourth the crescent is more open and the crown less transverse. 



The first true molar presents an increase in transverse extent of the 

 posterior external crescent, and the anterior one is a flattened cone. In 



