ARTIODAGTTLA. 719 



molars, and in the single external tubei'cle of the superior premolars. It is 

 referable to a family to be distinguished from the AnoplofherUdce by the pres- 

 ence of the external digits, and from that family, and from the Dichohunidce, 

 by the possession of tritubercular superior molars. It will be called the 

 JPantolestidce. 



The characters of the tarsus are of much interest, and demonstrate that 

 Pantolestes is the oldest type of Artiodactyle 3-et discovered, and that it is not 

 altogether primitive in some of its characters. Members of this order have 

 been found by Cuvier in the Upper Eocene {DicJiohune, Anophtherium, etc.), 

 but none have been determined as yet from the Suessonian of America. 

 A species represented by teeth from the Siderolithic beds of Switzerland 

 have been referred to Bicltobune (D. camjrichii Pict.) ; but dental characters 

 alone are not sufficient to distinguish that genus from Phenacodontidce. Dr. 

 Lemoine found astragali of a small Artiodactyle in the Suessonian of Reims, 

 and has referred them to his supposed Suilline LopJdochcerus peroni. I have 

 reported an astragalus from the Wind River formation of Wyoming Terri- 

 tory, which is almost exactly similar to those found by Lemoine. The 

 specimens of P. hrachjstomus enable me to characterize with some degree 

 of completeness this interesting form, which precedes in time all the known 

 American Artiodadyla. 



Pantolestes chacensis Cope. 



Systematic Catal. Vert. Eocene, New Mexico, 1875, p. 15. Report U. S. Geog. Surv. W. of lOOtli Mer., 



iv, ii, p. 146, pi. xlv, tig. 17. 



Plate XXIVd, fig. 5. 



The largest species, represented by four mandibular rami in the Big 

 Horn collection. It has the fourth premolar more robust and less trenchant 

 than in P. secans, and shorter than the last true molar. In P. secans it is 

 longer than the last true molar. For fuller description, see reference cited. 



Pantolestes metsiacus Cope. 



Proceed. Amer. Philos. Soc, 1881, p. 149, Paleontological BuUetiu, No. 34, p. 149, Feb. 20, 1883. 



Plate XXIVd, fig. 6. 



A small species of the size of the P. hngicaudus, and distinguished by 

 several peculiarities of dentition. The two cusps composing the anterior 

 internal lobe of the molars are quite distinct, but appressed. Each one is 

 connected with the external anterior lobe by a transverse crest, as is seen 



