2l6 THE HISTORY OF CREATION. 



broader and show very different structure from that seen 

 in the other two orders. Probably the Fish Dragons and 

 Serpent' Dragons developed as two diverging branches 

 out of the Prinifeval Dragons ; but it is also possible that 

 the Plesiosauria alone originated out of the Simosauria, 

 and that the lehthyosauria were lower off-shoots from the 

 common stock. At all events, they must all be directly, or 

 indirectly derived from the Selachii, or Primaeval fish. 



The succeeding classes of Vertebrata, the Amphibia and 

 the Amniota (Reptiles, Birds, and Mammals), owing to the 

 characteristic structure which they all exhibit of five toes 

 to each foot, may all be derived from a common primary 

 form, which originated from the Selachii, and which possessed 

 five toes on each of its four limbs. When we find a less 

 number of toes than five, we can show that the missing 

 ones must have been lost in the course of time by adapta- 

 tion. The oldest known Vertebrata with five toes are 

 the Batrachias (Amphibia). We divide this class into 

 two sub-classes, namely, mailed Batrachians and naked 

 Batrachians, the first of which is distinguished by the body 

 being covered with bony plates or scales. 



The first and elder sub-class of Amphibia consists of the 

 Mailed Batrachians (Phractamphibia), the oldest land 

 living Vertebrata of which fossil remains exist. Well- 

 preserved fossil remains of them occur in the coal, especially 

 of those with Enamelled heads (Ganocephala), which are 

 most closely allied to fish, namely, the Archegosaurus 

 of Saarbruck, and the Dendrerpeton of North America. 

 There then follow at a later period the gigantic Labyrinth- 

 toothed animals (Labyrinthodonta), which are represented 

 in the Permian system by Zygosaurus, but at a later 



