THE CARNIVORES 185 



The sectorial character of the first lower molar is almost com- 

 pletely absent. 



In the Bears as in the other families different species ex- 

 hibit various stages of specialization and adaptation but we 

 have already sufficiently emphasized this point in discussing 

 previous groups. 



The Pinnipedia 



The history of the aquatic Carnivora is almost a blank page 

 in paleontology and we know but little of their affinities. It 

 has been suggested that they are related to the early Creodonts. 

 Of late the Creodont theory has been displaced by one which 

 would derive them from some form related to the "Bear 

 dogs" of the Miocene but this suggested origin again is not 

 very clearly demonstrated. Certain resemblances which may 

 imply a relationship to the "Walrus have been pointed out by 

 Dr. Matthew in the Eocene Insectivore Pantolestes. We can 

 only say at present that there is no doubt that the forerunners 

 of this order were terrestrial Mammals with a typical and com- 

 plete dental formula and furthermore that it does not take 

 very long, geologically speaking, for a tritubercular molar to 

 retrogress into a simple conical tooth. 



Of the Pinnipedia there are three existing families, the Sea- 

 lions, Walruses and Seals, of which the last mentioned are in 

 general the most specialized. Nevertheless the Walrus has a 

 curiously aberrant dentition and in this feature must take the 

 place furthest from typical Carnivora. 



The Sea-lions, least aberrant of the group, are represented in 

 Fig. 66, which is an illustration of the jaws of the common 

 Gillespie's Sea-lion, Zalophus calif ornianus. This animal in its 

 general anatomical characters is the least removed of all the 

 Pinnipedia from the terrestrial Carnivora. In most members of 

 the suborder the milk teeth are shed about the time of birth, 

 but in Zalophus they remain in situ for a few weeks. The food 

 of this animal consists of fish, molluscs and sea-fowl. The 

 dental formula is: 



