JTo.S.J COPE ON EOCENE VERTEBRATA OF WIND RIVER. 195 



dental canal, which issues in a large mental foramen. This foramen is 

 situated near the middle of the vertical diameter of the expansion, and 

 below the anterior part of the diastema. It looks downwards and for- 

 wards. The external face of the posterior part of the ramus is nearly 

 plane. The inner face is vertical to a line which corresponds with the 

 inferior border in CorypJiodon, and then slopes obliquely outwards to the 

 inferior margin. The base of the coronoid process rises vertically from 

 the line of the alveolar border, and its external edge forms an anterior 

 border for the masseteric fossa. The inferior border of the fossa is not 

 defined. The inferior border of the ramus is decurved posteriorly, and 

 projects inwards considerably beyond the plane of the jaw. 



The premolars differ from the molars in having all their diameters ex- 

 cepting the vertical, reduced. The fourth premolar only differs from the 

 first true molar in the less elevation of the posterior border of the heel, 

 and in a little smaller transverse diameter. The external part of the 

 heel of the last molar rises into an obtuse cusp ; the remainder of the 

 border is tubercular. The heels of the other true molars end in simple 

 recurved transverse edges. On the premolars their posterior extremi- 

 ties are not recurved. The anterior face of the anterior cross-crest of 

 all the molars is concave, a,nd on the second premolar it looks obliquely 

 inwards. The posterior or second anterior inner cusp is obsolete on the 

 second premolar. The enamel on all of these teeth is, excepting where 

 worn, rather finely wrinkled. The first premolar is not preserved, but 

 its alveolus indicates that it is one-rooted and rather robust. The sizes 

 of the alveoli of the other anterior teeth are arranged in the following 

 order, commencing with the largest : 0. 5 1.2 5 1.3. The alveolus of 

 the canine is compressed, and has more than twice the anteroposterior 

 diameter of the largest incisor. The alveoli of the first and third are 

 subround ; that of the second is somewhat compressed. 



Measurements. 



M. 

 Length from the middle of the second incisive alreolus to the extremity of the 



last molar I95O 



Length of the series of consecutive molars 1170 



Length of diastema 0240 



Diameter of alveolus of Pm. 1 0090 



Diameter of alveolus of canine 0250 



Length of premolars 0460 



( vertical 0130 



Diameters of Pm. 11.^ anteroposterior 0130 



( transverse 0090 



r vertical 0120 



Diameters of Pm. IV< anteroposterior 0105 



(transverse 0120 



/ vertical 0100 



Diameters of M. I ) anteroposterior „ 0155 



(transverse 0110 



f vertical 0176 



Diameters of M. III..^ anteroposterior 02GO 



(transverse 0180 



