362 PALAEONTOLOGY AND EVOLUTION XI 



metacarpal is developed, but is much shorter than 

 the third, while the fifth is absent or rudimentary. 

 In this respect it resembles Anoplotkerium secunda- 

 rium. This circumstance, and the peculiar pattern 

 of the upper molars in Cainotherium, lead me to 

 hesitate in considering it as the actual ancestor 

 of the modern Tragulidce. If Dichobune has a 

 fore-toed fore foot (though I am inclined to 

 suspect that it resembles Cainotherium), it will 

 be a better representative of the oldest forms of 

 the Traguline series ; but Dichobune occurs in the 

 Middle Eocene, and is, in fact, the oldest known 

 artiodactyle mammal. Where, then, must we 

 look for its five-toed ancestor ? 



If we follow down other lines of recent and 

 tertiary Ungulata, the same question presents 

 itself. The Pigs are traceable back through the 

 Miocene epoch to the Upper Eocene, where they 

 appear in the two well-marked forms of Hyopopo- 

 tamus and Chwropotamus ; but Hyopotamus appears 

 to have had only two toes. 



Again, all the great groups of the Ruminants, 

 the Bovidce, Antilopidce, Camelopardalidw, and 

 Cervidce, are represented in the Miocene epoch, and 

 so are the Camels. The Upper Eocene Anoplo- 

 thcrium, which is intercalary between the Pigs 

 and the Tragulidw, has only two, or, at most, 

 three toes. Among the scanty mammals of the 

 Lower Eocene formation we have the perisso- 

 dactyle Ungulata represented by Coryphodon, 



