Posterior oblique view of fundus of right internal auditory meatus. The cochlea is anterior (toward the left side of the image); the bony labyrinth containing the semicircular canals is posterior (toward the right side of the image). The ampullae of the semicircular canals open into the vestibule as does the oval window. The fundus is the lateral (outer) aspect of the internal auditory canal where the facial and vestibulocochlear nerves branch into different compartments. In this view, the transverse (falciform) crest divides the meatus into a superior and inferior section. The superior or upper section is further subdivided by a vertical crest of bone (Bill's bar). While there is no similar bony crest subdividing the inferior section, a four quadrant fundus is conceptualized. Thus, the anterior superior quadrant contains the facial nerve; the anterior inferior quadrant contains the cochlear nerve; the posterior superior quadrant contains the superior vestibular nerve; and the posterior inferior quadrant contains the inferior vestibular nerve. (Image courtesy of AL Rhoton, Jr.)