234 



THE EYE IN EVOLUTION 



PLACODERMS^ 

 (all extinct) 



Fig. 241.— The Vertebrate Phylum 



AGNATHA 



Primitive 

 Fishes 



)-Lamprey~l Extant 



Hag JCyclo- 



J stomes 



.CHONDRICHTHYES 

 (Selachians and 

 Holocephalians) 



Poiypterini -^ 

 and sturgeons 



Bow-fin and 

 gar-pike 



OSTEICHTHYES 



I 

 Actinopterygii | Crossopterygii- 



Chondrostei 



Holostei 



I 



Teleostei 



(modern bony 



fishes) 



Rhipidistia 



Primitive - 

 AMPHIBIA 



I 



Primrtive 



REPTILES 



(Cotylosauria) 



— >Dipnoi 



Coelacanths 

 {Latimeria) 



f;"":;^ lExtant 

 Urodela > . , ., . 

 Apoda J Amphib.a 



-Chelonia\ 



Therapsida | Sauropsida->Sp/ienodon 

 Lizards 

 and 

 snakes 



Extant 

 Reptiles 



4 

 MAMMALS 



Archosauria -> Croco- 

 (Dinosaurs) diles 



I 



BIRDS 



EXTINCT VERTEBRATES 



(Drawn not to scale but to standard size) 



Agnathous Fishes 

 Pteraspis Cephnlaspis 



Placoderm 



Rhipidistian 



Prinutive 

 Ampb ■ '-n 



Primitive 

 Reptile 



Dinosaur, 

 Diplodocus 



