E. L. Troxell — Amynodonts in Marsh Collection. 21 



Aet. H.—Neiv Amijnodonts in the Marsh Collection; 

 by Edward L. Teoxell. 



[Contributions from tlie Othniel Charles Marsh Publication Fund, Peabody 

 Musemn, Yale University, New Haven, Conn.] 



Table of Contents. 



The Amynodontidae. 



Summary of species and relationships. 



Adaptations to physical environment and to feeding. 

 Description of new species. 



Metamynodon rex, sp. no v. 



Amynodon erectus, sp. nov. 



The Amtnodoxtid^. 

 Summary of Species and Relationships. 



Orthocynodon Scott and Osborn (1882, p. 22?>), Amyno- 

 don Marsh (1877, p. 251), and Metamynodon Scott and 

 Osborn (1887, p. 164) constitute a group of rhinoceros-like 

 ungulates found in America alone. Authors have placed 

 Cadurcotheriiim in the family Amynodontidse, apparently 

 on the basis of the great premolar reduction, but this 

 seems whollv inharmonious when we judge this genus 

 from the figures of its teeth (Abel 1914, p. 239). 



Metamynodon planifrons Scott and Osborn and M. rex, 

 sp. nov., come from the lower Oreodon beds, from a zone 

 of river sandstones characterized by and named from the 

 genus. Only two of these interesting specimens have 

 been described and but few skulls are known to exist. 

 The holotype of M. planifrons is in the Museum of Com- 

 parative Zoology at Harvard University; it consists of 

 a skull and jaws. A fine complete skeleton in the Ameri- 

 can Museum of Natural Historv has been fullv described 

 by Osborn (1898, pp. 80-94). 



The genus Amynodon is better known, because it is 

 represented by several species : A. (Orthocynodon) anti- 

 quus (Scott and Osborn) is found in the Middle Eocene 

 or Washakie; A. advenus (Marsh) and A. intermedins 

 Scott and Osborn, together with A. erectus, sp. nov., rep- 

 resent the Uinta beds of the Upper Eocene, and are in 

 general more advanced in their evolution. The Yale 

 specimens come from the region of White Elver, Utah. 



^ This is the first of a series of four articles on the rhinoceroses in the 

 Marsh Collection; the three others deal in turn with Hyracodon, CcBiiopus, 

 and Diceraiheriiim. 



