EVOLUTION OF THE PROROSCI1 )KA. 



is iu contact with the hinder border of the articular surface and helps to enclose the 

 external auditory meatus, just as in the elephants. The axis of the basis cranit is 

 parallel with that of the palate ; the palatines, pterygoids and alisphenoids are much 

 as in Elephas, but the basis cranii is more elongated and the occipital condyles are 

 more prominent. 



The Mandible (figs. 12 and L3). — The symphysis ©f the mandible is greatly 

 elongated, but still to a less degree than in Tetrabeloclon. It is somewhat decurved, 

 and its upper surface forms a spout-like channel, which is continued forward by 

 the procumbent and spatulate incisors (figs. 12 and 13). The angle is more prominent 

 and less rounded than in Tetrabeloclon, and the ascending ramus slopes backwards 

 to a less degree. The coronoid border rises from the outer surface of the jaw opposite 

 the last molar. 



. Drawn ^n&C. size. 



Figs. 12 and 13.— Mandible of Palceoimstodon beadnelli, Andrews. Upper Eocene. Egypt. 



The Teeth,— The dental formula is I. Gli C. ? • Pm - • M - 



1 2 ' " 3" 



The upper incisors (figs. 10 and 11) were laterally compressed tusks, bearing a 

 broad band of enamel on their outer surface and being downwardly directed It is 

 not known whether any trace of incisors, other than the tusks, existed. The anterior 

 upper premolar (Pm. 2) is a blunt simple cone with a slightly developed cingulum. 

 The next (Pm. 3) consists of a large outer cone and a smaller inner one arranged 



