The nervus olfactorius leaves the nasal cavity through the fenestra olfactorium advehens and enters the cranial cavity through its membranous wall i.e fenestra olfactorium evehens is absent. The nervus opticus enters the cranial cavity through the foramen orbitale magnum. The opposite nerves met together forming optic chiasma. The nervus octavus arises by a single root. The vestibular ganglion is located partially intracranially and partially in the foramen acousticum posterius. The ramus ampullaris anterior innervates the utricle and the anterior and lateral semicircular canals. The ramus ampullaris posterior innervates the lagena and the posterior semicircular canal. There is an independent saccular branch.