EVOLUTION OF THE PROBOSCIDEA. 



115 



similar. The two anterior molars are bilophodont, each transverse crest being composed 

 of a higher and more pointed outer cusp and a blunter and more worn inner one. 

 The postero-internal cusp is also prolonged backward into a small blunt lobe which, 

 when worn, gives rise to the pattern shown in the figure (fig. 15) ; the last molar is 

 bilophodont and has a small talon. 



The lower incisors have already been referred to. The cheek teeth are six in 

 number, the first premolar being wanting. The second premolar is a comparatively 

 small tooth, and is compressed from side to side. It consists of a large anterior cusp 



Fig-. 16. 



Mandible of Momtheriwm lyonsi, Andrews. M. Eocene. Egypt. 



behind which is a talon of considerable size. The third premolar is much larger ; it 

 consists of a high anterior portion and a posterior talon. The anterior part is composed 

 of three cusps, one of which forms the antero-internal angle of the tooth, while behind 

 this the other two are arranged transversely. The talon has a median ridge which 

 rises posteriorly into a tubercle. The fourth premolar the anterior cusp is less distinct, 

 but those forming the transverse ridge are better developed, especially the inner one. 

 The cusp on the talon is also larger than on the tooth in front. The first true molar 

 is bilophodont, each ridge consisting of two almost distinct tubercles. The cingulum 



Q 2 



