2732 



THE BONY FISHES AND GANOIDS 



The minute and rough scales make the skin like fine shagreen. A third genus 

 (Prionurus) differs in having a series of keeled bony plates instead of spines on the 

 sides of the tail. All the species of Naseus are said to be purely herbivorous. The 

 true surgeons use their spines as formidable weapons of attack by erecting them and 

 striking sideways with their tails. 



THE HORSE MACKERELS Family CARANGID^-E 



Although the name horse mackerel properly applies only to a single British fish 

 (Caranx trachurus), otherwise known as the scad, it may conveniently be made to do 



COMMON MACKEREL AND HORSE MACKEREL. 



(One-third natural size. ) 



duty for the whole of the members of the family to which that species pertains. Hav- 

 ing the body more or less compressed, these fishes are specially distinguished by the 

 teeth, when present, being villiform or conical. The spinous portion of the dorsal 

 fin is sometimes rudimental; the hinder rays of both the dorsal and anal may be 

 broken up into separate finlets, and when present, the pelvic fins are thoracic in 

 position. In the skeleton there are ten trunk and fourteen tail vertebrae, although 



