i6 



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 {PolyodontidcB) 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 

 praemaxillaries and no branchiostegal rays. The 

 Sturgeons {AcipenseridcB)^ 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, 



