in teleost fishes (Salmonoidei, Clupeiformes, Cypriniformes, and others), a scale having a smooth, rounded margin. Each scale lies in a deep pocket of connective tissue and overlaps its neighbor. Cycloid scales consist of two layers of non-cellular bony tissue: homogeneous tegumentary tissue and fibrous basal tissue. The tegumentary layer proliferates along the periphery in concentric stripes known as sclerites. The periodicity of sclerite formation, shown by annual rings, makes it possible to determine the age and growth rate of the fish. Radial nutrient ducts, which in Osteoglossidae form a complex alveolar structure, depart from the center of the scale.