1892.] NATURAL SCIENCES OF PHILADELPHIA. 297 



third, which is very large proportionately ; its talou is remarkable 

 for the entire absence of the entoconid; the bypoconid and hypo- 

 con ulid form very acute cusps upon the external and posterior 

 borders of the talon respectively, the valley of which thus opens in- 

 ward without obstruction. 



One species: C. {Chriacus) inversus Cope: Puerco. 



LOXOLOPHUSi Cope. 

 Syii. Chriacus Cope, in part. 



The superior molars are tritubercular with very minute hypocoue, 

 and are remai'kable for their autero-posterior as compared with their 

 transverse extent. The lower molars have a high trigonid with all 

 three cusps well developed and basin-shaped talon with elevated 

 hypoconid. 



One species: L. hyattianus Cope (Syn. Chriacus hyattianus^ Cope, 

 Loxolophus adapinus^ Cope). Puerco. 



TRICENTES* Cope. 

 Syn. Miochenus Cope, in part. 



This genus is very closely allied to Protochriacus, but differs in 

 the absence of Pj_. The premolars are compressed, acute, very high 

 and simple, except Rj which has a small deuterocone. M; anH ^ 

 have a nearly quadrate shape, produced by the well developed 

 hypocone and are surrounded by a stout cingulum. M3 is the 

 smallest of the series, the hypocone is absent and the metacone 

 reduced. The canine is large and separated from P2 by a consider- 

 able diastema. Inferior dentition unknown. The face is very 

 short and the anterior edge of the orbit is over the space between p* 

 and '"j. The forehead is fiat, the supraciliary ridges short and con- 

 verging rapidly to form the sagittal crest. 



Two species may certainly be referred to this genus : T. (Mioclw- 

 7ius) buccidentus Cope and T. crassicollidens Cope, Puerco. A third 

 species is doubtful, viz., ? T. (Mioclcenus) suhtrigonus Cope, in which 

 the number of upper premolars is not known, but the tooth struct- 

 ure agrees closely with Tricentes. Puerco. 



lAmer. Naturali'^t, 1885, p. 386. 



2 Loc. cit., p. 385, Trans. Am. Phil. Soc, Vol. XVI, Ft. II, p. 204. 



3 Am. Nat. 1885, p. 386. 



* Proc. Am. Phil. Soc, 1883, p. 31G. 



* Trans. Am. Phil. Soc, loc. cit., p. 304. 



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