364 O. C. Marsh— Vertebrate Life in America. 
not yet as complete as in the lineage of the Horse, this is not 
owing to want of material, but rather to the fact that the 
actual changes which transformed the early Tertiary pig into 
the modern Peccary were comparatively slight, so far as they 
ranches were so numerous as to confuse the line. It is clear, 
however, that from the close of the Cretaceous to the Post- 
Tertiary, the Bunodont Artiodactyles were especially abun- 
on this Continent, and only recently have approached 
extinction. 
metapodial bones were distinct. The type species of this genus 
was about as large asa cat. With Helohyus, this genus forms 
a well marked family, the Helohyide. 
In the Diplacodon horizon of the upper Eocene, the Seleno- 
dont dentition is'no longer doubtful, as it is seen in most of 
the Artiodactyla yet found in these beds. These animals are 
all small, and belong to at least three distinct genera. One of 
these, Homeryx, closely resembles Homacodon in most of its 
skeleton, and has four toes, but its teeth show well marked 
crescents, and a partial transition to the teeth of Hyopotamus, 
from the Eocene of Europe. With this genus, is another 
(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 
romeryx, which genus appears to be allied to the existing 
Deer family, or Cervide, and if so is the oldest known repre- 
sentative of the group. These facts are important, as it has 
