oG4j the geeat unknown. 



sence of remains of the latter in the tertiary dej^osits, is 

 sufficient evidence of their ncn-existence in our seas ; any 

 more than the general replacement of Placo'id and Ga- 

 no'id fishes by the Cycloids and Ctenoids, or the absence 

 of the former two from the tertiaries, is j)i'oof of their 

 present non-existence. 



It must not be forgotten, as Mr Darwin has ably in- 

 sisted, that the sj^ecimens we possess of fossil organisms 

 are very far indeed from being a complete series. They 

 are rather fragments accidentally jDreserved, by favouring 

 circumstances, in an almost total wreck. The Enalio- 

 sauria, particularly abundant in the secondary epoch, 

 may have become sufficiently scarce in the tertiary to 

 have no representative in these preserved fragmentary 

 collections, and yet not have been absolutely extinct.* 



But Professor Owen j^resses also the absence of any 

 recognised recent remains of such animals. Let us test 

 this evidence first by hypothesis, and then by actual fact. 



It may be that a true serpent, with large vesicular 

 lungs, would float when dead, and be liable to be seen by 

 navigators in that condition, or to be washed ashore, 

 where its peculiar skeleton would be sure to attract notice. 

 But, as I have before said, I do not by any means believe 

 that the unknown creature is a serpent in the zoological 

 sense. Would a Plesiosaurus float when dead ? I think 

 not. It is sujDposed to have had affinities with the whales. 



* I reason as a geologist, on geological premises, — reserving my own 

 convictions on the subject of prochronism, vi^hich would not aflfect this 

 argument. 



