1881.] Lib [Cope. 



Metalophodon testis, sp. nov. 



The genus Metalophodon was described by me in 1872.* Since that 

 time it has remained without further illustration of importance, as no good 

 specimens of it have been obtained by any of my expeditions up to the 

 present year. Thy material now at hand consists of the entire superior 

 molar series of the right side, and the superior molars of the left side, in 

 beautiful preservation. These display the characters on which the genus 

 was proposed, i. e., the conversion of the posterior external V of the 

 second 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 Coryphodontidm are carried further than in Coryphodon, 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, Manteodon, Coryphodon, Metalopliodon. 



Char, specif. — The first superior premolar has lost its crown. The other 

 premolars do not display any marked peculiarities. The internal cusps 

 are well developed, 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 in- 

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

 is subtriangular 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 Metalophodon. 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 differently proportioned. The part representing the 

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

 posterior Y. 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 ex- 

 ternal face of the V. There is also a small tubercle at the angle, where a 

 similar one is found in the corresponding tooth of Ectacodon ductus. 

 Altogether this tooth is like the posterior molar of Coryphodon elephantopus, 

 with a more prominent postero-external angle added. The anterior and 

 posterior basal cingula are well developed, the latter being strong in- 

 teriorly 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 



* Proceedings American Philos. Soc, 1872, p. 542. 



