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. 55. Right lower 
dentition of R. equi- 
nus; A, of a young in- 
- dividual; B, of an old 
Fig. 54. Left upper dentition, individual—r/2 natu- 
old individual—t1/2 natural size. 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 
21 mm. 
Skull, width across zygomatic arches [725mm 
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, 
U 
