78 Mr. Owen on the Zeuglodon Cetoides. 



!?aurian nature of the Zeuglodon, but it stands equally good for its cetaceous cha- 

 racter, as a section of the lower jaw of the Cachalot demonstrates. 



In the compressed shaft of the humerus (PI. IX.) and its proportion to the ver- 

 tebra, the Zeuglodon approximates to the true Cetacea, as much as it recedes from 

 the Enaliosauria ; but in the expansion of the distal extremity and in the form of 

 the articular surface, the humerus of the Zeuglodon stands alone. No one can 

 contemplate the comparative feebleness of this, the principal bone of the anterior 

 extremity, without feeling the justice of Dr. Harlan's conclusion, that the tail must 

 have been the main organ of locomotion of this stupendous denizen of the deep. 

 But assuming the humerus to have been part of the same skeleton with the ver- 

 tebra, and that this bone truly indicates the power and application of the vertebral 

 column of the Zeuglodon, can we suppose this flexible region of the spine to have 

 been encumbered with a sacrum and pelvis and hinder extremities ? 



To this conclusion we must arrive if we admit the correctness of Dr. Harlan's 

 determination of the bone which he has described and figured as the tibia. Now 

 in this bone, which is fortunately among the portions of the Zeuglodon brought 

 over by Dr. Harlan, the enlarged end, called distal, is fractured, so that no part 

 of the articulating surface remains ; and the projections, called internal and ex- 

 ternal malleolus*, are the results of accidental fracture. 



The texture of the bone is laminated and dense like the ribs. The whole frag- 

 ment presents a much less compressed form than we should expect to find in one 

 of the long bones of the arm or leg of a marine Mammal or Saurian, and it seems 

 to be a more probable conjecture, that it is a portion of one of the larger anterior 

 ribs than a bone of a hinder extremity. 



In recapitulating the chief points of evidence which, at present, can be brought 

 to bear on the question of the affinities of the Zeuglodon or Basilosaurus, it may be 

 stated, that the form of the humerus, though unlike that of any known vertebrate 

 animal, yet approaches much closer to the mammalian than to the saurian type ; 

 the vertebrae, which we have been enabled to examine, not only present a strictly 

 mammalian organization, but also the cetaceous modification of that type. The 

 teeth being of two kinds, some with single, others with double fangs, — being freely 

 implanted in distinct sockets, — consisting only of dentine and csement, and both 

 these presenting an intimate structure most closely resembling that of the same 



* Harlan, Ice. cit. p. 358. 



