[TA] the organ of balance; the three bony tubes of the labyrinth of the inner ear within which the membranous semicircular ducts are located; they lie in planes at right angles to each other and are known as anterior semicircular canal [TA] (canalis semicircularis anterioris [TA]), posterior semicircular canal [TA] (canalis semicircularis posterioris [TA]), and lateral semicircular canal [TA] (canalis semicircularis lateralis [TA]). SYN: canales semicircularis ossei [TA], bony semicircular canals.