850 THE WHITE KIVER FAUNA. 



The mandible is robust, and the symphysis is very steep in profile. 

 Its sutural face descends at an angle of 45°, and then exhibits a nigose 

 point of union below the first molar on the inferior border of the ramus. 

 The inferior border is subparallel with the tooth line, but presents an up- 

 ward concavity below the third molar. The coronoid process originates 

 opposite the anterior part of the third molar, is vertical and compressed. 

 The anterior border extends obliquely backwards. The masseteric fossa 

 has a prominent inferior border which extends upwards and forwards to 

 below the middle of the first molar. Its surface is gently concave below, 

 convex above. The ptei'ygoid fossa of the ramus is deep and large. Its 

 inferior border is a spur-like continuation of the inferior part of the ramus, 

 from which the thin outer wall of the fossa rises. The latter is somewhat 

 convex on the external side. The tooth basis and the incisive alveolar 

 sheath do not project much on the inner side of the ramus. The diastema 

 is as long as the tooth line, and the foramen mentale is below a point a little 

 behind its middle. The foramen dentale enters a little above the base of 

 the vertical ramus and three times the length of the last molar behind 

 that tooth. 



The superior incisor teeth are convex in front, the convexity slightly 

 oblique to the external side. The enamel is smooth and does not overlap 

 the sides. The crescents and cones of the molar teeth are well separated 

 from those of the same side by vertical fissures. A narrow crest connects 

 the base of each cone with the concave side of each crescent. The adjacent 

 horns of the two internal crescents join, and the connecting portion sends a 

 short crest into the interval between the external cones. The anterior and 

 posterior horns of the two crescents are produced transversely, forming the 

 anterior and posterior borders of the crown in the middle molar, the ante- 

 rior border of the third, and posterior border of the first molars. The an- 

 terior or fifth lobe of the first molar is simple. The inner and outer lobes of 

 the third molar are reduced in size, and close together. The last superior 

 molar is only half as large as the first, and the middle molar is interme- 

 diate in size. 



The molars of the inferior series do not difi'er in size so widely as those of 

 the superior series. They are subequal, but the anterior and posterior are 



