52 Annals of the Carnegie Museum. 



the two forming a perfect right angle; metapodials slender. Although 

 Palceosyops laliceps from the Bridger, and Telmatheriuni validum from 

 the Washakie appear, as Hatcher thought, to be the most likely 

 ancestors of the true horned types of the Uinta and the Oligocene, 

 it is rather questionable whether or not we may accept these as the 

 true ancestors of this line of the Titanotheriida^. The constant 

 progress of new discoveries in paleontology tends to make it more and 

 more apparent that the branches of the " phyletic trees" seem to 

 extend further and further back through the Tertiary strata in an 

 independent manner. 



Note. — The malar bone in the restoration, Plate X, has at the post- 

 orbital process been slightly increased in its relative perpendicular 

 diameter, because of the crushing sustained by the original. 



Carnegie Museum, 

 June 19, 1913. 



