68 
ACANTHOPTERYGII. — PERCAD^. 
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 ; 
c is from the belly. The concentric lines, it should 
be observed, are much more delicate and close 
than could possibly be engraved without greatly 
enlarging the scale. 
