THE PERCH TRIBE 



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by the body being cylindrical or somewhat depressed; while from two allied genera 

 they are distinguished by the maxilla or main upper jawbone being covered by the 

 preorbital bone, and by the premaxilla being free only at the side. The body is 

 elongate and nearly cylindrical in form, and the mouth is situated on the lower 

 surface of the thick and somewhat projecting muzzle. All the teeth of the jaws 

 are of small and uniform size, and teeth are present on the vomer and palatine 

 bones. The anal fin has but a single spine; although the margin of the propercular 

 bone is serrated, that of the preorbital is smooth; and the scales are small. These 

 fishes inhabit the Danube and certain other European rivers. 



LARGER AND SMALLER DANFBIAN PERCHES, AND RUFFE 

 (One-third natural 1 size.) 



Under this name, which belongs properly only to the British form, 

 may be included a few small perches, of which the typical representa- 

 tive {Acerina cernua) is shown in the lower figure of the above illustration. From 

 the other members of the family this and the allied genus Percarina differ by the 

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Ruffes 



