32 COPE 



Baseosts and axonosts well developed ; actino- 



trichia ; no fin-rays ; pectorals ? unibasal ; Haplistia. 



Baseosts rudimental ; fin-rays ; pectorals 



tribasal ; Cladistia. 



But one family is included in the Haplistia, the Tarasiidse, 

 from the Lower Carbonic of Scotland. The Cladistia are 

 represented by a family which is not known in the fossil 

 state, the Polypteridae of the rivers of Africa. The vertebrae 

 in this family are ossified and biconcave. 



Superorder Podopteeygia. 

 The superorder Podopterygia has also two orders. They 

 are thus defined : 



Branchiostegal rays present ; Lysopteri. 



Branchiostegal rays absent ; Chondrostei. 



In these orders the notochord is persistent, and there are 

 either actinotrichia, or fin-rays, which are more numerous 

 than the baseosts. Tail heterocercal or diphycercal. 



The Lysopteri includes four families, which differ as fol- 

 lows : 



I. Tail heterocercal. 



Teeth acute, external ; Palseoniscidse. 



Teeth obtuse, on palate and splenial ; Platysomidse. 



No teeth ; Chondrosteidse. 



II. Tail diphycercal. 



Teeth present ; scuta on body ; Belonorhynchidae. 



The Palseoniscidse range from the Devonic to the Jurassic 

 inclusive ; the Platysomidse belong to the Carbonic ex- 

 clusively ; the Belonorhynchidae to the Trias ; and the 

 Chondrosteidse to the Jurassic. 



The Chondrostei are degenerate representatives of the 



