200 THE WASATCH A^^) BRIDGER FAUNA. 



internal pterygoid muscle, etc. The two inferior are sublongitudinal and 

 subparallel. 



The crown of the superior third premolar is a slightly trihedral cone, 

 with a low cingulum on the inner side. The crowns of the last four molars 

 are transverse, narrowing to the internal rounded border. The fourth pre- 

 molar has two external conic tubercles, of which the posterior is the smaller, 

 and no cingula. The true molars have a low, interrupted, external cingu- 

 lum, and two external cusps. Of these the anterior is large, and behind it 

 is a small cingular cusp. The surfaces of the crowns are too much worn 

 to display the detailed structure. As in the mandibular series, the first true 

 molar is the largest tooth, from which the proportions diminish in both 

 directions. The crotvn of the tliird molav is not larger than that of the 

 third premolar. The molar bone is robust at the base, but becomes rapidly 

 attenuated and compressed. It has no postorbital angle. 



Measurements of jaws. 



M. 



Length of last five superior luolara 040 



Length of true molars O-ii 



T^• . „„ T> 1 :■: < anferoposterior ' Oi*(i 



Diainetors crown F-'ni. in •; ' 



I transverse .007 



T.. . T> • < anteroposterior 007 



Dinmeters crown P-ni. iv •; ' 



( transverse Oil 



Tx- » If • $ anteroposterior OOS 



Diaiueter.s crown M. i ^ ' 



i transverse Oil 



DiameterecrownM.iiiJ»"'*^^°P"«t'^"'"' ^ 



I transverse 008 



Lcnjjih of mandible from incisive border to edge of angle 1-22 



Length from incisive border to anterior basis of coronoid process 074 



Length of base of coronoid ]iroccss 033 



L(;ngth of syrai>hysis (oblique) 043 



Depth at P-ni. iii , 0J3 



Depth at M. iii 0->3 



Depth at condyle 037 



Width between inferior canines at base 007 



Diameter of base of inferior canine (long) 010 



Length of nndar series from canine 053 



Length of premolar series OM 



Diameters crown P-m. ni ^ ""teroposterior (oblique) 0075 



( transverse (oliliipie) ■ — .iXHi 



Diameters crown P-m. j,- ^ '""•'■'"P"''*''""'- "/" 



( transverse 007 



DiametersM.i J »""""1""" '■""■• "" 



( transverse <H)S.> 



The internal roots of the superior molars are jn-oduced inwards, giving 

 the crowns a strong internal support and extension at the base. The enamel 



