Scale is a skin derived thin bony or horny small plate that protecting the skin of most fishes and reptiles and usually overlapping one another.

In fishes, scales are bony, derived from dermis (inner layer >>>

Cycloid Scale

Thin, rounded, smooth-edged and disk like scale is called Cycloid Scale.

Found in most of all carps and similar fishes with soft fin rays. Arranged in an overlapping pattern. Consist of a rigid surface layer >>>