TRANSFORMATION OF ORGANS OF ANIMALS 61 



which extended from the neck to the wrist, and the 

 true wing membrane, which reached from the free 

 end of the little finger to the ankle. 



There are three essential types of Pterosaurians. 

 Pterodactylus, which had a short tail and teeth all 

 along the gape; 

 Rhamphory - 

 hnchus, which 

 had a long tail 

 and a beak set 

 in the front 

 part of the jaw 

 with teeth be- 

 hind it ; and 

 Pteranodon, 

 which had 

 neither teeth 

 nor tail. This 

 last type was 

 the most spe- 

 cialized of the 

 Pterosaurians, 

 and the strongest flyer of the whole group. They 

 attained to a huge size, the skull measurement averag- 

 ing 1 metre 20, and the wing extension 8 metres 30. 

 The modification which the fore-limbs of the Ptero- 

 saurians underwent in the course of their adapta- 

 tion to flight, was accompanied by degenerative 

 phenomena in proportion to the extent of the 

 specialization (see Pterodactylus spectabilis) (fig. 30). 



FIG. 30. Pterodactylus spectabilit (after Huxley, 

 Anatomy of V<rtebrated Animals). 



