Cope.] OiO [Oct. 7, 



Buuodonta and Selenodonta. The latter names are very expressive of the 

 dental characteristics of the two groups (tubercle and crescent bearing), 

 but not having priority, they have come into use as the adjectives buno- 

 dont and selenodont, to describe the types of molar crowns to which they 

 refer. But the divisions themselves can no longer be maintained, in view 

 of the numerous extinct forms now known to connect them. Not only 

 do transitions occur, but they occur at different points. Thus Dichobune 

 is the bunodout which corresponds with the selenodont Csenotherium ; 

 and Chojropotamus corresponds in the same way with Hyopotamus, An- 

 thracotherium standing between. If it be desirable to name the natural 

 groups into which the families fall, names enough exist in works on the 

 subject, but the divisions they have been applied to are not exactly in 

 accordance with the present writer's views of their true relations. These 

 are presented in the following table. In this work I have been much 

 aided by the Papers of Turner and Flower, which appeared in the Pro- 

 ceedings of the Zoological Society, of London, for 1850 and 1875 ; and of 

 Gill in Smithsonian Miscell. Collec. 1873. 



Before presenting the tables and phylogenetic diagrams, the author 

 wishes to make an explanation. Statements as to the phylogeny of a given 

 group, as family, or genus, are intended to apply to them as defined in the 

 present paper in the tables ; in other words, the phylogenies represent the 

 history of particular structures. There is a tendency among writers, even 

 with some of the best, in considering questions of phylogeny, to restrict 

 their attention to some particular species of a genus, or genus of a family, 

 and to consider all the minor peculiarities of said species or genus, whether 

 appropriate to the wider question before them or not. In brief, I have not 

 attempted to present any phylogeny of species. It will be long before we 

 have the necessary material for that. 



I. Superior molars tritubercular (Pantolestoidea). 



Molars bunodout ; four digits Pantolestidm. 



II. Superior molars quadritubercular with an intermediate fifth. 



I. Three digits (Anoplotheroidea). 



Intermediate tubercle anterior Anoplotheriidoi. 



II. Two or four digits (Anthracotheroidea). 

 A . The intermediate tubercle posterior. 



Four digits ; molars bunodout JDkhobtinido'. 



Four digits ; molars selenodont GcenotJieriidce. 



AA. The intermediate tubercle anterior. 



Four digits ; one series of V's below AntJiracotheriida!. 



Two or four digits ; two series of V's below XiphodontidcB. 



III. Superior molars quadritubercular, without an intermediate fifth. 

 A. Molars bunodont (Suoidea). 



Four digits ' Smdm. 



Two digits ElotheriidcB. 



