1892.] NATURAL SCIENCES OF PHILADELPHIA. 299 



The anterior lower premolars are small and feeble ; p^ is implanted 

 by a single fang and is separated by a diastema from p^, which has 

 two roots. J\ is much the largest of the series and consists of a 

 high, acute and trenchant cone with a strong cingulum, which forms 

 minute anterior and posterior basal cusps. The lower molars are 

 longer and narrower than the upper; the talon is larger than the 

 trigonid and the paraconid is much reduced or absent. M^3 has a 

 distinct hypoconulid. The mandible is long and stout, with regu- 

 larly curved inferior border and large, deeply marked masseteric 

 fossa. The zygapophyses of the lumbar vertebrie display the invo- 

 luted and interlockiug shape characteristic of the creodonts. The 

 manus is pentadactyl, plantigrade, and remarkable for the very 

 slight degree of interlocking of the metacarpals. The fibula is 

 very stout and forms an exceedingly massive external malleolus. 

 The astragalus is much like that of Arctocyon, but has a longer, 

 narrower and somewhat flatter trochlea and, as in that genus, is 

 perforated by a foramen. 



Two species are clearly referable to Chtnodon : C. {Miodcenus) 

 Jerox Cope, and C (^Miocl(jenus) corrugatus Cope. A third species, 

 C {Mioclcenus) protogonioides Cope, cannot be technically separated 

 from it, but the general appearance of the teeth is so different from 

 those of the typical species as to justify the suspicion that more com- 

 plete material w'ill cause its removal to another group. In j)artic- 

 ular, its resemblance to ? Trie.entes subtrigonus has been noted by 

 Cope. 



TETRACL^NODON, gen. nov. 

 Syn. MioL-lienits Cope, in part. 



Superior dentition unknown ; the inferior molars are like those of 

 Clcenodon, but the premolars are very different. The anterior ones 

 are relatively larger and more massive; p^ is a stout, compressed 

 cone and has a minute anterior basal cusp (paraconid) and a small 

 heel, which forms two basin-like depressions, divided by a median 

 ridge. P* has all the elements of a molar, with a massive protoconid 

 and small para- and deuteroconids ; the heel is low and composed 

 of two cusps (meta- and tetartocouids). The molars are constrncted 

 as in Cl(E)iodon, but are less rugose than in either of the undoubted 

 species of that genus. The humerus has a broad and flattened head, 

 small tuberosities and wide, shallow bicipital groove. The deltoid 

 ridge is very prominent and runs far down the shaft, which is stouter 

 than in Arctocyon. The trochlea is higher, thicker and narrower 



