n. the bony fluid-filled part of the inner ear that is concerned with hearing. Shaped like a snail shell, it forms part of the bony labyrinth. Along its length run three canals: the scala vestibuli, scala tympani, and scala media, or cochlear duct. The floor of the scala media is formed by the basilar membrane; the organ of Corti, which rests on the basilar membrane, contains the hair cells that act as auditory receptor organs. —cochlearadj.