39 



(Parameryx), also closely allied to Homacodon, but apparently a 

 straggler from the true line, as it has but three toes behind. 

 The most pronounced Selenodont in the upper Eocene is the 

 Oromeryx, which genus -appears to be allied to the existing 

 Deer family, or Cervidce, and if so is the oldest known repre- 

 sentative of the group. These facts are important, as it has 

 been supposed, until very recently, that our Eocene contained 

 no even-hoofed mammals. 



In -the lowest Miocene of the West, no true crescent-toothed 

 Arliodactyla have as yet been identified, with the exception 

 of a single species of Hyopoiamus ; but in the overlying beds 

 of the middle Miocene, remains of the Oreodoniidw occur in 

 such vast numbers as to indicate that these animals must 

 have lived in large herds around the borders of the lake-basins 

 in which their remains have been entombed. These basins are 

 now the denuded deserts so well termed Mauvaises Terres by 

 the early French trappers. The least specialized, and apparently 

 the oldest, genus of this group is Agriochcerus, which so nearly 

 resembles the older Plyopotdmus, and the still more ancient 

 Eomeryx, that we can hardly doubt that they all belonged to 

 the same ancestral line. The typical Oreodonts are the genera 

 Oreodon and Eporeodon, which have been aptly termed by 

 Leidy, ruminating hogs. They had forty-four teeth, and four 

 well developed toes on each foot. The true Oreodons, which 

 were most numerous east of the Rocky Mountains, were about 

 as large as the existing Peccary, while Eporeodon, which was 

 nearly twice this size, was very abundant in the Miocene of 

 the Pacific slope. 



In the succeeding Pliocene formation, on each side of the 

 Rocky Mountains, the genus Merychyus is one of the prevailing 

 forms, and continues the line on from the Miocene, where the 

 true Oreodons became extinct. Beyond this, we have the genus 

 Merychochmrus, which is so nearly allied to the last, that they 

 would be united by many naturalists. With the close of the 

 Pliocene, this series of peculiar ruminants abruptly terminates, 

 no member surviving until the Post-Tertiary, so far as known. 



