128 CLASSIFICATION OF AMPHIBIANS. 



Ichthyosaurus y and a snake ; it has the fins of the first, 

 the hody of the second, and the serpent-hke neck of the 

 last. It is no argument against this theory to urge 

 that there is a wide chasm between our fossil reptile, 

 provided with large paddles, and a true serpent; for 

 chasms, little inferior to this, occur in every department 

 of nature; and we must recollect that, in the Enalosaurij 

 we are treating of an order of animals whose foraier ex- 

 istence we only know of by theu' fossil remains. The 

 remark of M. Conybeare, that the Plesiosaurus, from 

 its structure, must have had many of those habits which 

 distinguish the swans, is fully confii-med by comparing 

 the circle of reptiles with the circle of the Natatores, or 

 swimming birds, which they in fact represent ; nay, so 

 beautifully and accurately do these groups typify each 

 other, that even the circle of the Anatidcd, or ducks, cor- 

 responds to that of the reptiles so far as this, that the 

 Enalosauri represent the AnserincB ; thus actually 

 bringing the Plesiosaurus and the swan into parallel re- 

 lations of analogy. If an arrangement, in short, is 

 natural, it will stand any test; and there, in the present 

 instance, are so many, and of such a diversified nature, 

 that by heedfully following this great principle of natural 

 affinity, we shall be guided through difficulties which 

 would otherwise be insurmountable. 



(128.) The station in nature of those wonderful rep- 

 tiles, the flying-hzards, or Pterodactyli, may be now con- 

 sidered. Were it not that natural groups are definite, 

 we might be tempted to think that in the class of rep- 

 tiles, at least, there was one more primary division than 

 in any other department of nature; and that this, which 

 would make the sixth, would be composed of the Ptero~ 

 dactyli. But we cannot for a moment seriously en- 

 tertain this behef ; opposed, as it is, to that uniform plan 

 upon which we see Nature has invariably proceeded in 

 every instance where her works have been sufficiently 

 studied. Rejecting, therefore, the hypothesis, that 

 the flying-hzards constitute one of the primary di- 

 visions of reptiles, our next question is^ to which 



