Most bony fishes have mouths at the front end of the head. These barbers are used to detect food. Bony fishes have separate incurrent and excurrent nostril openings. Most species of bony fishes are covered with and protected by a called scales. Some bony fishes may have scales only on portions of their body, and some species have no scales.
Scales lay head to tail in all bony fishes.
This helps reduce drag. True cosmoid scales are found only on extinct Crossopterygians. The inner layer of a cosmoid scale is compact bone. On top of this bone layer lies a spongy layer and then a layer of dentinelike material called cosmine. The upper surface is enamel.