26 THE ANGLER-NATUEALIST. 



small scales, such as the Eels. Occasionally the scales are 

 entirely covered by a soft thick cuticle, so as to be de- 

 tected only by close examination. 



There are four denominations of scales, named by M. 

 Agassiz — Cycloid, Ctenoid, Ganoid, and Placoid; (from the 

 Greek words eidos, signifying resemblance, and cyclos, a 

 circle, cteis, a comb or rake, ganos, brilliancy, and plax, 

 a flat, level surface). The first two of these include all 

 the most common forms of scales, and are marked with 

 circular or concentric lines, discernible through a micro- 

 scope, each line denoting a successive stage of growth by 

 the addition of a fresh layer — the smallest, or top layer, 

 having been first produced, and the others added under- 

 neath*. In the Cycloids these circular lines are smooth ; 

 whilst in the Ctenoids they are furnished with minute spiny 

 points, or teeth, which, however, usually wear ofi" on the 

 disc of the scale, and remain only on the posterior margin, 

 as shown in figure No. 2. 





^■fv-, 



(1.) Cycloid scale from back ot (2.) Ctenoid scale from lateral 

 Carp-Bream. line of Perch. 



The Ganoids have a hard, shining, enamelled surface, and 



* By steeping in water, the several layers or laminse of which scales 

 are formed can be separated with a delicate penknife ; and by means of 



