1 6 BRITISH FRESHWATER FISHES 



In the Chondrostean fishes found fossil in the 

 palaeozoic rocks the mouth, head, and scaling were 

 normal, but their modern descendants are very 

 remarkable. The Paddle-fishes (Polyodontida) of 

 China and the Mississippi have the body naked, the 

 eyes very small, the snout much produced, and the 



FIG. 3. Pelvic fin (a) and anal fin (b) of a Sturgeon. 

 b. basal cartilages ; r. radials ; d. dermal rays. 



mouth rather large and non-protractile ; there are no 

 prsemaxillaries and no branchiostegal rays. The 

 Sturgeons (Acipenseridce], with twenty or more species 

 from the seas and rivers of Europe, Asia, and North 

 America, differ from them especially in the presence 

 of a transverse series of four barbels on the lower side 

 of the snout, in front of the small, protractile mouth, 



