2 22 BRITISH FRESHWATER FISHES 



clavicles, but in some members of the order this 

 connexion has not been acquired, or has been lost. 



The fishes of this order which occur in the 

 fresh waters of our islands may be primarily- 

 divided into those with normal suborbitals and 

 those with the second suborbital produced across 

 the cheek to the prae-operculum. The former 

 includes the Percoids, or Perch-like fishes, and the 

 Mugiloids, or Grey Mullets and their allies. To the 

 latter group belong the Scorpaenoids and the Gastro- 

 steoids, which are dealt with in the next chapter. 



The Percoids, or Perch-like fishes, represent 

 the highest stage in the evolution of the normal 

 piscine type, although various aberrant offshoots 

 of the group have become adapted to peculiar 

 modes of life. 



The Perch family {PercidcE) includes a number of 

 fishes inhabiting the lakes and rivers of North 

 America, Europe, and northern Asia. The majority 

 of the species are little fishes found in the rivers 

 of the United States and known as " Darters," 

 whilst the largest members of the family are the 

 Pike-perches {Lucioperca), some species of which 

 attain a length of 4 feet, predaceous fishes closely 

 allied to the Perch, but more slender, and with a 

 larger mouth and stronger teeth. 



The Perch {^Perca fluviatilis) has the body some- 

 what compressed, and moderately elongate, tapering 

 posteriorly, with the back more or less humped 

 between the occiput and the dorsal fin ; the upper 

 part of the head is smooth and scaleless, whilst the 

 body is covered with small, rough, adherent scales. 

 The mouth is rather large, with pointed teeth in 



