ZOOLOGY. 173 



24. Perca. Perch. Body covered with rough scales ; edges 



of the gill-covers serrated ; gill-membrane seven rayed ; 

 ; dorsal Jins two, the first spiny, the second soft. 



25. Ilolocentrus. Gill-covers serrated, spinous, scaly ; 

 scales hard and rough ; in other respects agreeing with 

 the genus Perca. 



26. Bodianns. G?7/-^orer5 and habits like the last genus ; 

 scales smooth. 



27. Scomber. Mackrel. Head compressed, smooth ; gill- 

 membrane, SQyen rayed ; several small, spurious, prickly 

 Jins, between the dorsal Jin and the tail. 



Though not a very numerous family, the individuals of 

 some of the species are almost without number,particularly the 

 common Mackrel, which visits our coasts periodically in 

 such immense shoals, as to afford employment to a very large 

 part of the labouring population, resident on the coasts 

 where these fish are caught ; they appear early in the spring 

 and continue on the coasts during most of the summer 

 months ; the generally received opinion is, that the Mackrel 

 quits our seas during winter; but this is not satisfactorily 

 proved ; perhaps after spawning, they only quit the vicinity 

 of our shores, and retire to deep Avater, as repeated instances 

 have occurred of individual fishes being fished up from deep 

 water during the winter season ; in some places these fish are 

 caught by the hook and line, and in others, in nets of very 

 large dimensions ; all the species are gregarious, emit a phos- 

 phoric light, and may be eaten with safety. 



