558 THE WASATCH EPOCH. 



true molar into a transverse crest similar to that of the last true molar. It 

 follows that the first true molar is the only one which exhibits this V. It 

 also follows that in this genus the peculiarities of the dentition of Cory- 

 phodontkloe are carried further than in CorypJwdon, where two molars display 

 the V, and one the crest; or than in Manteodon, where all three have a V, 

 and none the crest. The genera then stand in the order of evolution, Man- 

 teodon, Coryphodon, Metalphodon. 



The first superior premolar has lost its crown. The other premolars 

 do not display any marked peculiarities. The internal cusps are well devel- 

 oped, and are most prominent posterior to the line of the apex of the 

 exterior crest. They connect with the posterior cingulum by a broad ledge, 

 but do not connect with the anterior cingulum. The two cingula nearly 

 connect round the inner base of the crown on the third premolar. 



The first true molar is well worn. The base of the posterior external 

 V can be seen, and the anterior and posterior cingula. There is no internal 

 cingulum. The second true molar is the largest of the teeth. It is sub- 

 triangular in outline, its external side forming, with the posterior, a right 

 angle. Its general character is much like that of the Coryphodontes, but it 

 presents the remarkable exception which constitutes the character of the 

 genus Metdopliodon. The posterior crest does not include a V, but is 

 straight, and consists of the same elements as the posterior crest of the third 

 true molars, but diff'erently proportioned. The part representing the ante- 

 rior V is a cone, much shorter than the part corresponding to the posterior 

 V. As there is a postero-exterior angle of the crown there is an oblique 

 surface rising to this part of the crest, which represents the external face of 

 the V. There is also a small tubercle at the angle, where a similar one is 

 found in the corresponding tooth of Edacodon cindus. Altogether this tooth 

 is like the posterior molar of Coryphodon elephanfopus, with a more prom- 

 inent postero-external angle added. The anterior and posterior basal cingula 

 are well developed, the latter being strong interiorly to the point where it 

 sends a branch upwards to the internal cusp. There is no internal cingulum. 

 The last superior molar is a transverse oval, more regular than usual in 

 the species of Coryphodon, since the diameters of the internal and external 

 portions are about equal. The characters of the posterior crest differ from 



