16 



ORDERS OF MAMMALIA. 



which is expressed by the generic name. The species of 

 Zcugloclon are Eocene and Miocene, one of the best known 

 being the great Z. cetoides of the Middle Eocene (Jackson 

 Beds) of the United States, which attained a length of 

 seventy feet. 



By Professor Huxley, Zeuglodon is regarded as in some 

 respects intermediate between the true Cetaceans and the 



Fig. 622. — Zcnglodon cetohlr<. a, ifdlar tnnth, natural size ; B, VerteVira, reduced. 

 From the JliJdle Eocene of Nortli America. (After Lyell.) 



Carnivorous family of the Seals. On this point this eminent 

 naturalist remarks : " The skull of this great Eocene sea- 

 monster, in fact, 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 pKemaxillary bones, 

 which take a full share in bounding the forepart 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 

 form of the snout, the long symphysis, and the low coronary 

 process of the mandible, are approximations to the Cetacean 

 form of those parts." 



The genus Sqiudodon is nearly related to Zeuglodon, but 

 the teeth are more numerous ; and the double-fanged molars 

 (fig. 623) are more compressed and pyramidal in form. " The 

 nasal bones are very short, and the upper surface of the 

 rostrum presents the groove, filled up during life by the 



