Fish scales - are the remnants of the bony armour which enveloped the very earliest fish. Fish have scales as a protective coated for the skin. In fact, not all fish have them. But we usually think of a fish as a cold blooded, aquatic animal that swims by means of fins breathes by means of gills and is covered with scales. Scales may be of four different kinds placoid, granoid, cycloid and ctenoid. Placoid scales are long, spiny and toothlike, and the made of enamel and dentine. These are found on fishes which have a backbone made of gristle, such as sharks and rays. Ganoid scales are rather like placoid scales but are mainly bony and covered with kind of enamel called Ganoin. These think scales are found especially in garfish. Cycloid scales are thin, large, round or oval scales arranged in an overlapping pattern. They are found in carps and similar fishes.
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