CARTILAGINOUS FISHES BONY FISHES 1) Their endoskeleton is primarily made of cartilage.1) Their endoskeleton is entirely made of bone. 2) Their exoskeleton is made of placoids.2) Their exoskeleton is made up of cycloids or thin bony plates. 3) The position of their tail is heterocercal.3) Their tail fin is homocercal. 4) They have 5 gills that are overly exposed (no operculum).4) They have an operculum on either side of their gills.5) In them the fertilization is through internal mechanisms.5) They fertilize their eggs externally. 6) Eg- dog fish, electric ray torpedo and sharks.6) Eg- fying fish, globe fish and sea horses.