324 



GEOLOGY. 



so until the tropical regions of t ho Old World are more fully studied, 

 for the chief evolution seems to have taken place there. No remains 

 of lemuroids or of their descendants have been found in the Pliocene 

 beds of North America. In Europe, all such remains thus far recovered 



Fig. 466. — Teeth of mastodon {Mastodon longirostris) , showing slightly worn tubercles 

 at the right and much worn ones at the left. (From Gaudry, after Kaup.) 



have been limited to the middle and southern portions, a limitation 

 which is hardly accidental, and which probably implies that the cli- 

 mate of northern Europe was already becoming uncongenial to the 

 primates. There are indeed signs of a gradual abandonment. The 



Fig. 467. — Teeth of elephant (Elcphus primigenius) , with the transverse ridges differ- 

 entially worn, showing dentine in the center, the enamel, which forms the crenu- 

 lated loops, supported by dentine within and cement without. (After Owen 

 and Metcalfe.) 



Paidopithex, a representative of the higher apes, seems to have left 

 Europe in the earlier Pliocene. The lower apes (Cercopithecidce) 

 remained longer, and the Macacus (the Barbary ape) still lives on the 

 rock of Gibraltar. The Macacus appears to have had considerable 



