495 
THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
common ancestor of the Bridger age is all that such a view postulates I have 
elsewhere suggested that the Bridger representative of the oreodonts may be the 
very imperfectly known genus Hdohyus. The same formation has yielded teeth 
of a similar type, but considerably larger, which may well represent the ancestor of 
Ancodiis. lhat the genus has not yet been reported from Europe is not surprising 
in view of the very scanty Eocene fauna as yet knoAvn in that region. The indica- 
tions, at present known, all go to show that Ancodus, Oreodon, and Agriochosrus 
represent three divergent branches of the same artiodactyl stem, the starting point 
of which will prove to be some middle Eocene genus with pentadactyl feet and teeth 
of the type of Helohyus. Probably the agriochoerid and oreodont lines diverged 
from each other somewhat later than Ancodus did from both, though, in view of 
the extraordinary specializations which Agriochoerus exhibits, this view is uncer- 
tain, and a decision upon it must await the event of future discoveries. 
The possibility of an American origin of Ancodus must not be overlooked. 
No one can imagine that we have yet obtained more than an insignificant fragment 
of the Uinta fauna, and the number and variety of Bridger artiodactyls are far 
greater than the described genera would lead one to expect; this is indicated by 
numerous remains which, unfortunately, are too fragmentary for satisfactory iden- 
tification. While the facts at present known all seem to point to the origin of 
Ancodus in the Old World and its migration to America, in the interval between 
the Eocene and the Oligocene (Uinta and White River), yet until the American 
artiodactyls from the middle and upper Eocene are far better known than at present, 
such a conclusion cannot be regarded as final. 
