AGE OF MAMMALS. 



267 



first appear in the Tertiary strata. Not a species of fish, 

 or reptile, or bird, or mammal of the Tertiary period 

 is in existence at the present time. These classes of an- 

 imals are in contrast with mollusks in this respect, for 

 many of the latter, as you saw in 368, coming into ex- 

 istence in the Miocene and Pliocene periods of the Ter- 

 tiary, are living still in the midst of the mollusks of the 

 present period that were created long ages after them. 



376. Fishes. The remains of fishes abound in the ter- 

 tiary strata. The most interesting are the Shark family, 

 which flourished in great numbers both in Europe and 

 America. Some of them were monstrous in size. In 

 Fig. 160 is represented the tooth of the Carcharodon 



\^gr 



Fig. 160. 



