1892.] NATURAL SCIENCES OF PHILADELPHIA. 295 



even their ordinal position, is very obscure, the teeth being of that 

 generalized and primitive character to which all taammalian types 

 of dentition converge, as we trace them back in time. 



OXYCL^NUSi Cope. 

 Syn. Mioclttnus Cope,- in part. 



Only upper dentition known. The anterior premolars form sim- 

 ple, compressed and trenchant cones; on 1^4 there is also a well 

 developed deuterocone. The molars are simply tritubercular, with 

 small, erect and acute cusps. ^2 is the largest of the series, espe- 

 cially in the transverse direction. The para- and metacones arise 

 close to the outer side of the crown, the latter somewhat nearer to 

 the median line. The protocone is the largest of the elements. 

 There is no distinct hypocone, merely a thickening of the cingulum 

 at that point, which is most marked in m^. Minute but very dis- 

 tinct proto- and metaconules are present. M3 is very much reduced 

 in size and more oval than triangular in shape, but preserves all the 

 cusps. 



One species: 0. {Mioclcenus) cuspidatus Cope. Puerco. 



CHRIACUS3 Cope. 

 Syn, Pelycodus Cope, in part. 



The dentition of this genus is very much like that of the primitive 

 lemuroids, to a genus of which some of the species were originally 

 referred. The character of the symphysis, the spacing of the inferior 

 premolars and the presence of the paraconid, being the only impor- 

 tant differences. The upper premolars have compressed and acute 

 protocones and on P3 ""^^ 4 are well developed deuterocones. The 

 upper molars are triangular in shape and much extended trans- 

 versely ; "^1 has a small hypocone and '^ a hypocone and an addi- 

 tional cusp io front of the protocone, which in accordance with 

 Osborn's system of nomenclature, we may call the protostyle; ^ is 

 the smallest of the series and has neither hypocone nor protostyle. 

 The anterior lower premolars are simple and spaced apart, but P4 

 has a deuteroconid and heel. In the molars the trigonid is much 

 higher than the talon and the paraconid is reduced ; the talon also 

 has three cusps, of which the hypoconulid on m^ is in some species 

 enlarged and carried on a distinct fang. 



1 Proc. Amer. Phil. Soc, 1883, p. 312. 



^ Tran>. Am. Phil. Soc, Vol XVI, Pt. II, p. 320. 



^ Ptoc. Am. Phil. Soc, 1883, p. 313. 



