otolith

An otolith, (lithos, a stone), also called statoconium or otoconium is a structure in the the inner ear, specifically in the vestibular labyrinth. The saccule and utricle, in turn, together make the otolith organs. They are sensitive to gravity and linear acceleration. Because of their orientation in the head, the utricle is sensitive to a change in horizontal movement, and the saccule gives information about vertical acceleration (such as when in an elevator).