SUBCLASSES 



DEVONIAN FISHES OF IOWA 

 Class AGNATHA 



69 



ORDERS 



FAMILIES 



1. CYCLOSTOMI 



2. OSTRACOPHORI 



1. Hyperotreta or Myxin- 



oidea 



2. Hyperoartia or Petromy- 



zontes 



1. Heterostraci 



2. Anaspida 



3. Osteostraci 



4. Antiarchi 



[Unknown as fossils] 

 [Unknown as fossils] 



Coelolepidae 



Paammosteidae 



Pteraspidae 



f Birkeniidae 



I Euphaneropidae 



f Ateleaspidae 

 \ Cephalaspidae 



Asterolepidae 



Class PISCES 



SUBCLASSES 



ORDERS 



SUBORDERS 



1. ELASMOBRANCHII 



2. HOLOCEPHALI 



3. DIPNEUSTI 



4. TELEOSTOMI 



f 1. Pleuropterygii 

 | 2. Ichthyotomi 

 -j 3. Acanthodii 



4. Selachii 



1. Chimaeroidei 



1. Ctenodipterini 



2. Sirenodei 



3. Arthrodira 



1. Crossopterygii 



_ 2. Actinopterygii 



Asterospondyli 

 Tectospondyli 



1. Haplistia 



2. Rhipidistia 



3. Actinistia 



4. Cladistia 



f 1. Chondrostei 



J 2. Protospondyli 



I 3. Aetheospondyli 



I 4. Isospondyli. &c. &c. 



