68 ACANTHOPTERYGII. — PERCADiE. 



and appear to feed at the "bottom, on Loach, 

 Miller's Thumb, and testaceous mollusca." 



The scales of the Perch have their hinder, 

 or free edge, set with fine crystalline points, ar- 

 ranged in successive rows, and overlapping. Their 



SCALES OF PERCH. 



front side is cut with a scolloped pattern, the 

 extremities of undulations of the surface that 

 radiate from a common point behind the centre. 

 These undulations are separated by narrow fur- 

 rows, across which, contrary to the ordinary rule, 

 the close-set concentric lines that follow the sinu- 

 osities of the outline are not visible. Under the 

 microscope they look as if they had been split in 

 these radiating lines, after the whole number of 

 layers had been completed, and that the fissures 

 had then been filled with new transparent sub- 

 stance. The engraving above represents scales 

 selected from different parts of the body of a 

 Perch, and magnified* a is from the back ; h is 

 from the lateral line, and shows the tube for the 

 passage of the lubricating mucus well developed ; 

 e is from the belly. The concentric lines, it should 

 be observed, are much more delicate and close 

 than could possibly be engraved without gieatly 

 enlarging the scale. 



