Complex sentence: Ctenoid (toothed) scales are like cycloid scales with small teeth along their outer edges, and are usually found on fish with spiny fin rays, such as the perch-like fishes.
Split into simpler sentences: Ctenoid (toothed) scales are like cycloid scales with small teeth along their outer edges. They are usually found on fishes with spiny fin rays, such as the perch-like fishes.