XI PALEONTOLOGY AND EVOLUTION 351 



or, perhaps, linear types between the VivcrridcB 

 and the ffycenidce. 



Hardly any order of the higher Mammalia 

 stands so apparently separate and isolated from 

 the rest as that of the Cetacea ; though a careful 

 consideration of the structure of the pinnipede 

 Camivora, or Seals, shows, in them, many an 

 approximation towards the still more completely 

 marine mammals. The extinct Zeuglodon, how- 

 ever, presents us with an intercalary form between 

 the type of the Seals and that of the Whales. 

 The skull of this great Eocene sea-monster, in 

 tact, shows by the narrow and prolonged inter- 

 orbital region; the extensive union of the parietal 

 bones in a sagittal suture ; the well-developed 

 nasal bones ; the distinct and large incisors 

 implanted in premaxillary bones, which take a 

 full share in bounding the fore part of the gape ; 

 the two-fanged molar teeth with triangular and 

 serrated crowns, not exceeding five on each side 

 in each jaw ; and the existence of a deciduous 

 dentition its close relation with the Seals. 

 While, on the other hand, the produced rostral 

 !' rm of the snout, the long symphysis, and the 

 low coronary process of the mandible are approxi- 

 mations to the cetacean form of those ]> 



The scapula resembles that of the cetacean 

 Jf'/pcroodon, but the supra-spinous fossa is lar 

 and more seal-like; as is the humerus, which 

 differs from that of the Cetacea in presenting true 



