392 THE PCTERCO EPOCH. 



direction and less closeh* placed. On the inner sides the sculpture may 

 disappear with age, but never on the external .side. 



In their unworn state the internal cinguluni-crest of the premolars 

 is coarsely serrate. They extend round the external cone to the posterior 

 base, and to the outer base anteriorly, so as to aj)pear as a wide oblique mar- 

 gin projecting antciior to the cone, on an external view. The external cone 

 is compressed at the apex. The first superior premolar is unknown. No 

 external cingula on the premolars, but a distinct one on the external base 

 of the true molars. The latter have no internal cingulum, but there is one 

 on both the anterior and po.sterior bases of the crowns which extend from 

 the anterior and posterior internal tubercles, respectively. The two tuber- 

 cles last mentioned ])roject farther inwards than the median internal tuber- 

 cle, and are distinguished from it on the inner face of the crown by grooves. 

 All the tubercles, including the external, ha\-e a subround section. The 

 intermediate tubercles are the smallest, the other four being subequal. The 

 jiremolars are remarkably large as compared with the true molars; the dis- 

 proportion being greater in this than in niiv mammal known to me, except 

 the Tetraconodoii of Falconer. 



The crowns of the inferior premolars are convex on the external side, 

 and flat on the inner. Tlie principal and external cone is compressed 

 at the apex in the anterior three premolars. The internal cusp is flat, and 

 appressed to the external, and its apex is joined to the side of the latter. On 

 trituration the two speedily become confluent, while the anterior and pos- 

 terior basal lobes remain distinct, forming two lesser areas. The first infe- 

 riiir premolar is a simple cone flattened on the inner side, and with a 

 low posterior heel. Of the four principal tubercles of the inferior true 

 molars the anterior external is the largest, and extends a little farther ante- 

 riorly than tlie anterior internal. The anterior tubercle is on the inner 

 side of the middle. On tlie last molar, the heel may have one or two acces- 

 sory tubercles. 



The ramus is moderately robust and compressed. The inferior outline 

 extends to the incisive border by a gentle slope, and rises below tin- last 

 molar teeth. The masseteric fo.ssa is well marked in front, but has no dis- 

 tinct posterior or inferior l)oundary. The su])erior true molars are placed 

 Well posteriorly, or rather the; orl)it is anterior, for its anterior border is 



