THE MAMMALIA OF THE UINTA FORMATION. 507 



in most of the particulars, partly owing to the fact that it was diawii up before tlie 

 type specimen had been removed from the matrix and put too^ether, and in this way, 

 even after examining the type ourselves, as Prof. Mai'sh kindly allowed us to do, we 

 were formerly led to consider the Bridger species as a distinct genus {Orthocynothm). 



A second examination of the type specimen recently made brings out several 

 important diagnostic characters in addition to those already noted in oin- i)reliminary 

 bulletin, p. 262. There are three lower and probably three upper incisors ; the first 

 lower premolar is wanting. The canines are erect. There are rugose postorbital, 

 antorbital and infraorbital processes. The nasals are very short and slightly over- 

 hang the anterior narcs. The type of A. antiquus is still found to resemble that of 

 A. adi'enus closely, with the important exception that there are four lower premolai-s 

 instead of three, the first lower premolar being fully functional and bifanged ; the 

 first upper premolar is missing. It may subsequently be found to represent a distinct 

 genus as we at first supposed, for which the original name Ortliocynodon would stand. 

 The -.i. intermedius, besides its much larger size, may be clearly distinguished from 

 the two foregoing by the jirocumbent position of the canines and by the retention of 

 a single fanged first upper jjremolar. 



These and other characteristics throw a new light upon the phylogenetic jjosition 

 of the Amy nodonl idee, which will be discussed later. 



AMYNODONTID.E S. & 0.* 



Rhinoceros-like animals extending from the Middle Eocene to Lower Miocene ; 

 skull deeply excavated in front of orbit ; incisor border very broad; nasals short and 

 hornless ; canines and incisors present and functional in both jaws ; pattern of the 

 molars like that of the rhinoceros except for the non-reduction of the external crest 

 of the third upper molar; probably four t(jcs in fi-ont and ihree behind; proliably 

 astragalus rests upon the cuboid as in the ihinoceros. 



This defmition is considerably modified from that previously given by the writers, 

 in order to embrace the Miocene genus. 



The genera embraced in this family are: 



Lower Miocene ( White Hivei-). 



Metamvnodon,! nobis. Dentition, i. 1., c. I, pm. 3, m. '. ' Ui)pcr and lower 

 canines obrKjuely placed, the latter fitting sonu'wlial inti'rnal to the former when the 



• E. M. Museum Bullniii, No. :i. 1H8:(. p. 4. 



\ lliillcliii ni' thf iMiiNfiiiii 111' C<>iii|>nmlivi- Znology, Sf|il., \>->sT, l>. 105. 



