20 



ELEPHANTS. 



enormously increased, but lias not yet invaded the root' of the 

 skull, so that the sides are only separated by a sharp median 

 crest. The posterior surface of the skull slopes forward above 

 the condyles, and there is a deep pit in the middle line for the 

 attachment of the muscles necessary to support the increasingly 

 heavy head. 



Of the incisor teeth in the upper jaw only the second pair 

 now remains, and these have been still further enlarged, forming- 

 Fig. 10. 



Posterior lower molars (m 2 ,m a ) of (A) Moerithenum^ (B) Palvomastodon, 

 showing- the increase in the number of ridges of Palceomastodon. 

 I nat. size. 



downwardly directed, curved, somewhat flattened tusks with a 

 broad band of enamel along their outer sides only. The 

 canine has disappeared, but there are still three premolars 

 replacing milk-molars. The anterior premolar is a simple 

 cone, while the crown of the posterior one consists of two 



