RHYNCHIPPUS EQUINUS 



97 



between the premolars and the succeeding molars, being 

 only slightly rhomboidal in outline, while in the last two 

 molars the anterior external corner is markedly prolonged. 

 In different individuals, the lower jaw varies greatly in 

 height, but this seems to me to be individual and sex varia- 

 tion. The three incisors and the canine are subequal in 



Fig. 54. Left upper dentition, 

 old individual 1/2 natural size. 



Fig. 55- Right lower 

 dentition of R. equi- 

 nus; A, of a young in- 

 dividual; B, of an old 

 individual 1/2 natu- 

 ral size. 



size, closely crowded, and each with a small cingulum near 

 the base of the enamel. 



MEASUREMENTS OF SKULL, SPECIMEN 3191 



Skull, length from front of nasal to back of lambdoidal crest 211 mm. 



Skull, width across zygomatic arches 172 mm. 



Skull, width across postorbital processes 78 mm. 



Skull, height above molar 2 84 mm. 



Dentition, from upper inc. I to molar 3 140 mm. 



Dentition, from lower inc. i to molar 3 136 mm. 



Mandible, height under molar 2 35 mm. 



Mandible, height under the articulation 118 mm. 



