CLASSIFICATION OF VERTEBRATA 



Super-CLASS GNATHOSTOMATA, Haeckel 



With visceral arches, one pair of which is modified into 

 jaws. 



With an anterior and a posterior pair of limbs. 

 Amphirhinal. 



I. CLASS ICHTHYES 



Anamnia. Anallantoidea. With fin-limbs. The median 

 fins are supported by skeletal elements. 



1. Sub-CLASS PISCES 



Eespiring by gills only. Heart entirely venous. Nasal 

 blind-sacs not communicating with the mouth. 



I. Division ELASMOBRANCHI^Qno^^iQ. With seven, 

 six, or mostly five, pairs of branchial arches, enclosing as many 

 gill-clefts. The gill-bearing clefts are separated by complete 

 septa, which are continuous with the outer skin. 



Vertebrae with chorda-centra, unless still acentrous. 



Without membrane bones. Skin with numerous small 

 enamelled denticles. 



Males with a pair of mixopterygia. 



1. Order Proselachii. Mouth subterminal, without a 

 rostrum. 



With archipterygium biseriale. 

 Vertebrae still acentrous. 



Pleuracanthus (Xenacanthus) Decheni. Lower Permian 



and Carboniferous. 



Cladodus. Lower Carboniferous. Fins with almost 

 preserial archipterygium. 



2. Order Plagiostomi, Dumeril. Mouth transverse and 

 ventral, with a rostrum. 



With Ichthyopterygium preseriale. 

 Pectoral fins separated from the head. 

 1. Sub-order SELACHII. Numerous since the Carboni- 

 ferous mountain Limestone. 



