THE WHALES AND PORPOISES 235 



The example which we have chosen to represent the toothed 

 Whales is the common Porpoise, Phocaena communis, the diet 

 of which consists exclusively of fish. Inspection of Fig. 83 

 shows that the jaws are long and relatively weak and that 

 the teeth are small, similar, very numerous, with spade-like 

 crowns and constricted necks. The enamel organs are not 

 much developed and the teeth consist of a special type of den- 

 tine with a coating of cement. Some Odontocetes possess very 

 few teeth and some, like the Dolphin, more than twice as many 

 as the Porpoise figured. 



The great number of similar cylindrical teeth of the toothed 

 Whales is only approached in certain Armadillos in Avhich the 

 teeth lack enamel entirely and are the result of a much more 

 ancient specialization. It is in the toothed Whales that we see 

 secondary increase of cheek teeth at its maximum. 



