INTRODUCTION. : 



cartilaginous fishes, are so thick, through being covered 

 with skin similar to that of the body, that their rays are 

 completely hidden ; excepting in such instances, in which 

 there is a spine inserted in the fore part of the fin. This 

 spine being quite, apparently, intended for purposes of 

 offence and defence, is naked and partially unattached to 



Fig. 2. DORSAL FINS OF AUSTRALIAN FISHES. 



1. Rock Whiting. 



2. Australian Salmon. 



3. Sergeant Baker. 



4. Estuary Perch. 



5. Mullet. 



6. Goat-Fish. 



7. Horse Mackerel. 



8. Nannygai. 



9. Herring'. 



the other rays. The Port Jackson Sharks will serve as 

 an illustration of fishes having this find of dorsal fin. 



The anal fin usually corresponds in position with 

 the second dorsal ; being situated on the under part of 

 the tail, behind the vent. In a great measure, it will be 

 found to depend for its length upon the size of the tail ; 



