INTRODUCTION. 



1 1 



In a general way fish-scales are separated into two 

 great divisions ; cycloid-scales and ctenoid-scales. 



Cycloid scales are those which have a smooth pos- 

 terior margin, and a more-or-less concentric striation of 

 the surface. In addition to some others, such scales are 

 usually found on soft-rayed fishes (Parrot-fishes, for 

 instance). 



Fig. 4. TYPES OF CYCLOID SCALES. 



Upper Body Scale of ROCK WIIITISO. Lower Body Scale of AUSTRALIAN GRAYLING. " 



(Both {treat ly magnified.) 



Ctenoid scales have their posterior margin rough or 

 toothed ; and such scales are characteristic of spiny-rayed 

 fishes; though cycloid scales occur on some (Mullets and 

 others). 



