Section 81: The chorda tympani (ct) can be seen near the petrotympanic suture (pts) at the anterior end of the middle ear space. The anterior mallear ligament (aml) is visible anteriorly; this is the most important stabilizing structure for the malleus (m). The antrum (ant) is surgically defined as the large air cell lateral to the horizontal semicircular canal. The lateral wall of the antrum is the petrosquamous suture (pss) (Körner's septum) internally. The basal turn of the cochlea (c) is just becoming visible. fi - fossa incudis.