HISTORY OF THE fAMBLYPODA 451 



History is a highly interesting skull of \Bathyopsis, which will 

 shortly be described by Professor Osborn. The premaxillaries 

 have not been preserved, and it is therefore impossible to say 

 whether the upper incisors had already been suppressed or not, 

 and though the upper canine has not been found, there can be 

 no reasonable doubt that it was a tusk. The lower canine had 

 not yet gone over to the incisor series, but was a thin though large 

 tusk. There was one more lower premolar, four in all, than 

 \Uintatherium possessed, and all the premolars were some- 

 what smaller and simpler than the molars. The small skull 

 had a broad and somewhat concave cranial roof, with slightly 

 raised enclosing crest, and the horn-like protuberances of the 

 posterior and median pairs were present in an incipient stage. 

 Whether those of the nasal pair were also indicated is not 

 known, but probably they were not. The lower jaw was of 

 very pecuUar shape ; the flange of the inferior border was not 

 so well defined as in ^Uintatherium, but had no hinder margin 

 and rose very gradually backward. 



The series of genera in descending order, '\Eobasileus, 

 ]Uintatherium, ^Elachoeeras and ^Bathyopsis, immediately 

 impresses the observer as being a natural phylogenetic series 

 of successive ancestors and descendants. Unfortunately, 

 only the skull is known in the two last named, but there is no 

 ground for supposing that the discovery of the skeletons would 

 require any alteration in the series as we now have it. No 

 member of this series has yet been found in the Wasatch, but 

 there can be no doubt that it was represented in that stage, for 

 a recent expedition from the American Museum has collected 

 teeth of a '\Bathyopsis-\ik.e form in still older beds. 



SUBORDER fPANTODONTA 



During the older part of the lower Eocene the f uintatheres 

 must have been a rare and unimportant element of the fauna, 

 at least in those parts of the continent whose history we know. 

 Their place was taken by another suborder, the fPantodonta, 



