144 



CARNIVORES. 



tooth is taken by two complete simple teeth. Hence it is obvious that we have 

 here a case where an originally single tooth divides into two distinct but simpler 

 teeth. This may not at first sight seem a fact of much importance ; but in reality 

 it serves to show how the numerous simple teeth characteristic of the toothed 

 whales may have been derived by the splitting up of teeth originally composed of 

 three distinct cusps like those of the leopard-seal ; each cusp of such a tooth forming, 

 as we shall see, a distinct tooth in the whales. 



The Crested Seal. 



Genus Cystophora. 



The remarkable-looking animal represented in the accompanying illustration, 

 and commonly known as the crested, hooded, or bladder-seal (Cystophora cristata), is 



the chested seal (^5 nat. size). 



at once distinguished from all the other members of the family by the casque-like 

 prominence crowning the fore-part of the head. This seal, together with the 

 under-mentioned elephant-seal, differs from all the species yet noticed in having but 

 thirty teeth, owing to the reduction of the incisors to two pairs in the upper, and 

 to one pair in the lower jaw. In both the cheek-teeth are small and simple, with, 



