CHAPTER V 



THE MILLER'S THUMB AND STICKLEBACKS 



The Miller's Thumb — Distribution — Habits — The Three-spined Stickle- 

 back — Appearance — Habits — Distribution — The Ten-Spined Stickle- 

 back. 



Eighth Sub-Order : Acanthopterygii Cotto-scombriformes : The 

 Bullhead and Mackerel-like Spiny-finned Fishes. 



Having disposed of the three members of the Perch 

 Family inhabiting the fresh waters of Great Britain, we have 

 to descend a long way in the classified scale before reaching 

 the next fish found in our streams and lakes. This brings 

 us to the eighth sub-order of Acanthopterygii^ distinguished by 

 Dr. Giinther as Cotto-scombrifonnes^ the bullhead and mackerel- 

 like sub-order, which is arranged in fifteen families, embracing 

 fish of most diverse, and often of very grotesque, aspect. The 

 John dory, the tunny, the weever, the angler or fishing- 

 frog, and the gurnards are among the best known members 

 of these families, and differ from each so widely in habits and other 

 appearance that it may puzzle the student at first to understand 

 how they can be classed together under any " natural " system. 

 It must be confessed that, just as the whole order of spiny- 

 finned fishes do not form a perfectly consistent group, so 

 this sub-order presents some puzzling anomalies. One fin at 

 least is always spinous ; but the spinous dorsal fin is not 

 always present, and in some families the spines have become 

 modified into tentacles, as in the hideous fishing-frog or 

 sea-devil {Lophius\ and even into suctorial discs, as in the 



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