It lies in the auditory capsule of the skull. It is useful for maintenance of equilibrium. In the fish external and middle ears are absent. Internal eats covered by cartilaginous labyrinth. A space is present between membranous and labyrinth is filled with perilymph.
The membranous labyrinth shows laterally compressed sac. It is divided into utriculus and sacculus. At the end of the sacculus lagena is present.
From the dorsal side of the internal ear duct arises. This is called saccus endolymphaticus. It opens out on the skin.
In the ampullae sensory patches are present, they will be acoustic in nature, in the utriculus and sacculus otholiths are present. They are mainly useful for maintenance of balance. Thus the internal ear is useful for caring and maintenance of balance.