COXDYLAETHRA. 497 



the posterior external apex. This one turns inwards at its posterior ex- 

 tremity, which is on the posterior cingulum. 



The anterior angle or horn of each external crescent of the true molars 

 is very prominent. They are sections of short vertical ridges, which unite 

 near the base of the crown, giving abruptness to the impression of the 

 external surface of the anterior lobe. The middle of each face has a faint 

 median ridge. The two molars have an anterior basal cingulum, but no 

 posterior or internal, excepting a trace between ■ the bases of the internal 

 lobes. The anterior intermediate crescent is quite parallel with the ex- 

 ternal; the anterior internal tubercle has a slightly V-shaped section. The 

 posterior inner tubercle is quite confluent with an oblique intermediate 

 crest, as in 31. chamense. In the last true molar, as there is only one 

 internal tubercle, this crest is short, terminating at the posterior border. 

 The last true molar is like the last premolar, except in its two impressed 

 external crescents. Enamel smooth. 



Measurements of superior molars. 



M. 



Length of superior molars, less Pm. i 046 



Length of true molar series 028 



Length of base of Pm. ii .' 005 



Diameters of base Pm.iii^^'^t'''-"P«^t'^"'"' 006 



( transverse 007 



Diameters of base Pm. iv ^ ^"**=^°P°^*«"°' 008 



< transverse 010 



Diameters of base M. ii 5 anteroposterior Oil 



c transverse 013 



There are some variations in the characters of the fourth superior pre- 

 molar. In the specimen above described, which is the one on which the 

 species was based, the external face of the crown is uninterrupted, and 

 there is a weak cingulum round its internal base. In another specimen 

 there is a narrow vertical ridge distinguishing the two lobes on the external 

 face, as is found in the true molars, but less developed, and the internal 

 cingulum is strong In another specimen with the external ridge, there is 

 no internal cingulum. 



A characteristic of this species is the great contraction of the pre- 

 molar series. This condition in an imperfect specimen led me to suspect 

 in first describing the species that the fourth inferior premolar was only the 



third. The inferior incisors, canines, and premolars form an uninterrupted 

 32 c 



