AMERICAN RUMINANT-LIKE MAMMALS. 257 



eventually prove to be the fountain head whence these diverg- 

 ing streams were derived. Homacodon is of a very generalized 

 type and seems to approximate the European genus DicJiobiuie, 

 which Schlosser regards as the remote ancestor of the Pecora. 

 But the European genus is not known with sufficient complete- 

 ness to make it plain whether it should be included in the 

 same family as Homacodon or not. The latter is very primi- 

 tive in structure, and has an unreduced dentition with rela- 

 tively large canines, simple premolars, and sexituberculate upper 

 molars which are just beginning to assume the selenodont pat- 

 tern ; the feet are probably pentadactyl. Nothing is known 

 of Homacodon which can militate against the view that it 

 represents a family whence were derived the various seleno- 

 dont lines that have become distinctly segregated in the Uinta 

 and widely diversified in the White River. 



The probable ancestor of Homacodon is Trigonolcstes {Pan- 

 tolestes) of the Wasatch, a little creature which, having typi- 

 cally artiodactyl feet, possesses an extremely primitive type of 

 dentition, so much so that, when only the teeth were known, 

 the genus was supposed to be a lemuroid. In Trigonolcstes we 

 perhaps have the ancestor of all those selenodonts which I have 

 described as indigenous to North America. It is of interest 

 that one little character which persists throughout all the later 

 genera of the group is already present in the Wasatch type ; 

 namely, the coossification of the meso- and ecto-cuneiforms in 

 the tarsus. 



The table on the following page will show conveniently the 

 mutual relationships of the various selenodont genera as 

 presented in what has been said. 



If these results ' are well founded, we shall have to regard 

 the Tylopoda as a highly important and eminently character- 

 istic group in the history of mammalian life on this continent, 

 a group which was very ancient, very peculiar, very long-lived, 

 and greatly diversified, and one which in these respects may 

 sustain a comparison with the Pecora. Admitting these facts, 

 it becomes well-nigh impossible to define the suborder. As 

 originally limited and defined by Flower, the demarcation is 

 easy enough, because the definition is taken from the existing 



