THE SEA-SAURIANS EXTINCT. 331 



to different individuals of a species which I had previously 

 proved to be an extinct whale ; a determination which 

 has subsequently been confirmed by Professors Miiller 

 and Agassiz. Mr Dixon, of Worthing, has discovered 

 many fossil vertebrae, in the Eocene tertiary clay at Brack - 

 lesham, which belong to a large species of an extinct 

 genus of serpent (Palceophis), founded on similar verte- 

 brae from the same formation in the Isle of Sheppey. 

 The largest of these ancient British snakes was twenty 

 feet in length ; but there is no evidence that they were 

 marine. 



" The sea saurians of the secondary periods of geology 

 have been replaced in the tertiary and actual seas by 

 marine mammals. No remains of Cetacea have been 

 found in lias or oolite, and no remains of Plesiosaur, or 

 Ichthyosaur, or any other secondary reptile, have been 

 found in Eocene or later tertiary deposits, or recent, on 

 the actual sea-shores ; and that the old air-breathing 

 saurians floated when they died has been shewn in the 

 Geological Transactions, (vol. v., second series, p. 512.) 

 The inference that may reasonably be drawn from no 

 recent carcase or fragment of such having ever been 

 discovered, is strengthened by the corresponding absence 

 of any trace of their remains in the tertiary beds. 



"Now, on weighing the question, whether creatures 

 meriting the name of 'great sea-serpent' do exist, or 

 whether any of the gigantic marine saurians of the 

 secondary deposits may have continued to live up to the 

 present time, it seems to me less probable that no part of 



