322 PROCEEDINGS OF THE ACADEMY OF [1892. 



lianus Cope and 3f. turgidunculus Cope, all from the Puerco. The 

 systematic position of the genus is very doubtful, for such premolars 

 are quite unknown among the creodonts, and are entirely like those 

 of the condylarthrous family, Pert/jii/c/wdoe. Indeed, if. opisthaciis 

 was at one time referred to Hemithlceiis^. On the other hand, the 

 structure of the molars is quite different from that of any of the 

 typical Condylarthra, and if, as Schlosser has suggested, it becomes 

 necessary to refer Mioclcenus to that group, it will form a very dis- 

 tinct family of the order. 



PEOTOGONODON gen. nov. 

 Syn. MiodcEnus Cope, in part. 



To this genus I refer as a type species the M. pentacus which Cope 

 provisionally incorporated with Iliocloenus, though directing atten- 

 tion to the resemblance of its inferior molars (superior unknown) to 

 those of the phenacodont Protogonia, from which it differs in the 

 simplicity of p^, which has no deuteroconid. Certain specimens, how- 

 ever, show rudimentary indications of it. I think there can be no 

 doubt that this genus is referable to the Phenacodontidce. A second 

 species, P. (Mioclcenus) lydekkerianus, the structure of p* in which is 

 not known, probably belongs to the same genus. Puerco. 



PARADOXODON gen. nov. 

 Syn. Chriacus Cope, in part. 



This curious form, the systematic position of which is altogether 

 uncertain, is known only from inferior molars, though the alveoli of 

 the premolars indicate that these teeth were extremely compressed 

 and recall in their proportions those of the primitive artlodactyls ; 

 the molars also suggest relationship to that group. The latter 

 increase in size from the first to the third and the trigonid rises very 

 little above the talon. In mTi the proto- and metaconids are of 

 about the same size and on the some transverse line ; they are both 

 compressed and the protoconid shows a tendency to become cres- 

 centic ; the small paraconid is placed immediately in front of the 

 metaconid from which it is separated by a slight notch, while a low 

 ridge connects it with the protoconid ; the hypoconid is also some- 

 what crescentic, the entoconid lower and more conical. In m^ the 

 trigonid is curiously asymmetrical, which is caused by the backward 

 inclination of the metaconid, the larger size of the paraconid than 



1 Tert. Vert., p. 407. 



