148 



TELE OS TOMES 



Fig. 148. 

 bichir. x J. 



The Nile bichir, Polypterus 

 White Nile. (Modified after 



Dors aspect. B. view of throat re- 



gion, showing jugular (gular) plates and ven- 

 tral elements of the dermal shoulder girdle. 



reduced, implanted with- 

 in body wall. Includes 

 Chondrosteans (" Gan- 

 oids ") and Teleocephali 

 (" Teleosts "). 



I. CROSSOPTERYGIANS 



The CROSSOPTERYG- 

 IANS, as palaeontology 

 has demonstrated, are 

 the most ancient Tele- 

 ostomes. In their struct- 

 ural characters espe- 

 cially in the fins, skeleton, 

 nervous system they 

 are clearly to be sepa- 

 rated from the neigh- 

 bouring Ganoids. And 

 their transitional charac- 

 ters have not as yet been 

 clearly demonstrated. 



Polypterus (Figs. 148, 

 A, B, 149) and its kindred 

 genus, Calamoichthys 

 (Fig. 150), stand alone 

 as the survivors of the 

 Crossopterygian group. 

 They have diverged but 

 little from their Devo- 

 nian kindred, and demon- 

 strate in the most inter- 

 esting way the persistent 

 survival of fishes. From 



