WEALDEN FORMATIONS. 15 



The reverse of all these conditions is seen in the bones of the hind limbs of the 

 Iguanodon and other Dinosaurian reptiles. 



If one takes the pleasure of speculating on the genesis of Didus or Dinomis, guiding 

 or reining the roaming fancy by facts, the geographical limitation of such ornithicnitoid 

 species, and their primitive association exclusively with creatures of which they could have no 

 dread, suggest the more obvious and intelligible hypothesis of derivation from antecedent 

 birds of flight, whose wings they still show more or less aborted, according to Buffon's 

 principle of transmutation by degeneration, — with a progressive predominance of the legs 

 over the wings, ultimately resulting in a maximization of the terrestrial and abortion of 

 the aerial instruments of locomotion. 



