10 



FISHES OF AUSTRALIA. 



In the Gurnards and Flying-Fishes (particularly the 

 latter) the pectoral fins have undergone a tremendous in- 

 crease in size, being large and almost wing-like; in the 

 case of the Flying-Fishes, being particularly adapted for 

 sustaining them for a short time, while they are making 

 their flying-leaps through the air. 



Though usually of a soft character, the rays of pec- 

 toral fins are sometimes supported by a large and strong 

 spine; this being particularly prominent in the Catfishes, 

 in which it is very powerful and barbed ; becoming a 

 weapon of defence. 



In Sharks and Rays, the pectoral fins are highly- 

 developed, being very large. In the Rays (where they 

 are usually termed either "wings" or "flaps") they are so 

 large as to appear to be a part of the body itself ; in most 

 cases all the outward traces of a fin being altogether lost. 



The ventral fins rank next to the pectorals in general 

 importance, their particular function being that of keeping 

 the fishes upright in the water. They represent the hinder- 

 limbs of mammals and birds. 



In the Eels the ventral fins are completely absent.* 



Scales : The skin of fishes is usually covered with 

 scales of some description. In some instances however, 

 these are either rudimentary or entirely absent; while in 

 others (such as certain Leather jackets, Sharks, Rays, 

 etc.) they are replaced by hardened skin-projections or 

 papillce which give to the surface a velvety or shagreen- 

 like appearance. In addition to these, in certain instances 

 (the Porcupine-Fishes and some Toad-Fishes) the skin 

 is more or less enveloped with a covering of sharp, thorn- 

 like spines ; while in others, such as the Knight-Fishes, 

 a coat of mail consisting of bony plates, completely in- 

 vests the fish. 



Scales are of great importance to a fish in the amount 

 of protection that they give to its skin ; while to the 

 student of fish-life their number, structure and arrange- 

 ment are highly-valuable characters for the determination 

 and classification of the fishes themselves. 



* In some Eels the pectorals also are absent. 



