SUPPOSED AFFINITIES OF THE FISH-LIZ ABDS. 127 



eminent observers, on the affinity of the Enalosauri to 

 the class Pisces, seems to us conclusive on the subject ; 

 more especially as this affinity receives full confirmation 

 from our own theory of the principle of variation in this, 

 and in all other natural groups. Hence it follows that 

 these extinct reptiles united the three aberrant divisions 

 of vertebrated animals into one circle ; namely, the rep- 

 tiles, the Amphibia, and the fish. But the situation 

 which we have assigned to the Ichthyosaurus, may be 

 tested in other ways ; thus, for instance, every natural 

 group has one of its aberrant divisions entirely aquatic : 

 fish among vertebrated animals, whales among the Mam- 

 malia, and the swimming order (^JVatatores) among birds, 

 are some among innumerable proofs that this prin- 

 ciple is universal ; each of these groups, in short, sym- 

 boHcally represents the other, and sometimes this is 

 carried so far, that we do not know whether the resem- 

 blance is one of analogy or of affinity. As to the sup- 

 posed connection between the Ichthyosaurus and the 

 crocodiles, the two groups correspond to each other in 

 being typical of their respective circles, and they should 

 therefore, from theory, possess some few characters in 

 common ; but we must always recollect that the one, like 

 quadrupeds, are walking animals ; and that the other, 

 like fishes, are provided with fins : they cannot there- 

 fore be brought together, or, at least, following one an- 

 other. 



(127.) The preceding remarks will serve also to explain 

 much of what appears anomalous in the structure of the 

 Plesiosaurus. The affinity which this extraordinary 

 reptile bears to the marine tortoises, as we have already 

 seen, has been observed both by Cuvier and Conybeare ; 

 while its close relation to Ichthyosaurus is perfectly un- 

 questionable. Now if we were called upon to imagine 

 some animal which was to connect the fish-lizards to the 

 ophidians or serpents, we could not devise any form 

 better calculated to fill up the gap than that which 

 nature presents to us in the Plesiosaurus: it seems, in 

 fact, compounded of three distinct animals— -a turtle, an 



