VEJRIEBKATA 



27 



;!-4 



From these tables it appears that the Seiachii with grind- 

 ing teeth are prior in geological age to those with teeth 

 especially appropriate to a carnivorous diet. The latter 

 reached their greatest perfection, as well as size and num- 

 bers, in the Neocene system, some of the Carcharodons hav- 

 ing been probably seventy feet in length. 



All the families of Elasmobranchii are common to the 

 Old and New Worlds. 



