Chondrichithyes
1. Mostly marine with a heterocereal tail.
2. Endoskeleton cartilagenous.
3. Skin with placoud scale.
4. Gills 5-7 pairs without opercula.
5. No air badder or lungs.
Osteichthyes
1. Developed bony fish with homocereal tail.
2. Endoskeleton bony.
3. Skin with mucosglands, ganoid, cycloid ot ctenoid scales.
4. Gills four pairs with opercula.
5. Swim bladder present.