508 THE MAMMALIA OF THE UINTA FORMATION. 



jaw is closed. The second, third and fourth upper premolars of the molar pattern. 

 Postglenoid and posttympanie processes widely united. Periotic not exposed. 



Upper Eocene ( Uinta). 



Amtnodon* Marsh. Dentition, i. % c. I, pm. |:f, m. f. Upper and lower 

 canines erect or obliquely placed. The third and fourth premolars of the molar pat- 

 tern. Postglenoid and posttympanie processes separated. Digits : 4-3 (Marsh). 



A. ADVENUS Marsh. Premolars f. JSTamber of upper incisors uncertain. Up- 

 per canines obliquely placed, lower canines erect. 



A. iNTERMEDius, spcc. nov. Premolars *; first upper premolar rudimentary and 

 single fanged. Canines in both jaws very large, semi-procumbent, oval in section. 

 Three functional upper incisors. 



Middle Eocene ( Washakie). 



A. (Orthocynodon) antiquits, nobis. Premolars I ; first upper premolar bi- 

 fanged. Canines in both jaws vertical, triangular in section. Number of upper and 

 lower incisors uncertain. Mastoid portion of periotic exposed. 



AMYNODOlSr INTERMEDIUS. 



Plate X. 



This species is represented by the base of the anterior portion of a skull (No. 

 10,309) in beautiful preservation, showing the complete characters of the teeth, the 

 palate, the position of the orbit and the lowei- portion of the premaxillaries. The four 

 canines and an upper molar of another individual are preserved. Part of the lower 

 jaw and a premolar of a third, and the mandibular symphysis of a fourth. There are 

 also numerous skeletal fragments, which however cannot be referred to Amynodon 

 with any certainty. 



Dentition (Figs. 10, 10a). The three incisors arc equidistant ; the median one 

 is slightly larger than the lateral and is placed about as far from the premaxillary 

 suture as the lateral incisor is from the canine. The crowns are pointed, convex on 

 the anterior and posterior faces, and slightly compressed laterally. The canines are 

 very powerful, with lance-shaped crowns and a decidedly flattened oval, quite unlike 

 the trihedral cro>yns in A. antiquns ; they project forward at angle of forty-five de- 

 grees, and slightly outwards ; the fangs are powerful and deeply rooted beneath the 

 first ])remoUir. There is a considerable diastema. 



» Aim. Jimr. S<i. iiiul Art-, Scpi., 1877, p. 2")1. 



