English: Ganoid scales of the Carboniferous fish, Amblypterus striatus. (a) shows the outer surface of four of the scales, and (b) shows the inner surface if two of the scales. Each of the rhomboidal ganoid scales of Amblypterus has a ridge on the inner surface which is produced at one end into a projecting peg which fits into a notch in the next scale, similar to the manner in which tiles are pegged together on the roof of a house.