TRANSACTIONS OF WAGNER 



UINTA SELENODONTS 



ancestor of Agriocliccnis, and that Protorcodon paradoxiais is merely a connect- 

 ing link between the former and the oreodonts. Its structure thus tends to 

 confirm the conclusion that the two families have a common origin, and that 

 the numerous points of resemblance between them are not simply instances of 

 parallel development. 



(2.) If these conclusions are well founded, it follows that the likeness of 

 the upper molars of AgriocJurriis to those of the anthracotheres — a likeness to 

 which attention has repeatedly been directed — is not due to any near relation- 

 ship between the groups, but has been independently acquired. The molars 

 of Protagriochceriis, despite the presence of the fifth cusp (protdconule), are less 

 like those of Ancodus than are the molars of its White River successor. The 

 peculiar arrangement of the incisors, canines, and caniniform lower premolars, 

 which is so highly characteristic of the agriochoerids and oreodonts, is already 

 fully established in the Uinta genera of these families. Consequently, to find 

 a common ancestor of the agriochcerids and the anthracotheres (in which the 

 canines are normal), we should have to go very far back indeed, so far that the 

 peculiar features of the anthracothere dentition would probably not yet have 

 begun to appear. 



(3.) As we cannot yet point out the Bridger ancestor of the oreodonts, 

 of course it is not yet possible to identify the common ancestor of both fami- 

 lies. However, from the close approximation between Protorcodon and Pro- 

 tagriochceriis, it is altogether probable that the common ancestral form will be 

 found in the Washakie or the Bridger proper. It is further probable that this 

 unknown genus will prove to be very nearly related to the forerunners of Pro- 

 iylopiis, Lcptoreodon, etc., and may perhaps even be a member of the same 

 family. Further than this it is unsafe to speculate, for the interrelationships 

 of the various Uinta selenodonts are very complicated and difficult to unravel, 

 their likenesses and unlikenesses being combined in such puzzling ways, but 

 the peculiarities of the canines and premolars would indicate that Lcptoreodoii 

 and Caniclomcryx lead back to this common ancestor of the oreodonts and 

 agriochoerids, and that this ancestor, while very nearly allied to the forerunner 

 of Protylopits, was yet in Bridger times generically distinct. To those who 

 are familiar with the remarkable appearance of Agriocha'rus, with its extra- 

 ordinary clawed feet, it may seem altogether unlikely that this genus can have 

 been derived from a Bridger ancestor, common also to the oreodonts. When, 

 however, Agriochcer7is is carefully studied, every portion of its skeleton, not 

 even excepting its extraordinary feet, is found to bear witness of its relation- 



