scale, in zoology, small plate or shield forming part of the outer skin layers of certain animals. Scales provide protection from the environment and from predators. Fish scales are formed of bone from the deeper, or dermal, skin layer. The elasmobranchs (e.g., sharks) have placoid scales, which are bony, spiny projections with an enamel-like covering. Ganoid scales, which are found on such fishes as gars and the bowfin, are similar to placoid scales but are covered with a peculiar…