INTRODUCTION 



CLASSIFICATION AND TAXONOMY 



Fishes defined. Classification of British freshwater fishes : 

 the Teleosteans. Topography of the fish : the head the mouth 

 the teeth the gills the pharyngeals the scales the fins 

 coloration the air-bladder. Measurement and counting 



THE word fish is often applied in a popular sense 

 to any animal which lives in the water, but 

 zoologists use the name only for aquatic animals which 

 belong to the great group of Vertebrates, which have 

 a skull and a backbone, a brain and a spinal cord. 

 All Vertebrates which live in the water are not 

 fishes, but only those which propel and balance 

 themselves by means of fins and obtain oxygen 

 from the air dissolved in the water by means of 

 internal gills. 



The classification of the British freshwater fishes 

 adopted in this work is as follows : 



Class MARSIPOBRANCHII. 

 Order HYPEROARTII. 



Family Petromyzonidse {Lampreys}. 

 Class PISCES. 



Subclass CHONDROSTEI. 

 Order SELACHOSTOMI. 



Family Acipenseridae (Sturgeons). 



