ANATOMY OF THE NASAL PASSAGE AND ASSOCIATED STRUCTURES OF NEOPHOCAENA PHOCAENOIDES

The nasal passage and associated structures of thirteen specimens of Neophocaena phocaenoides taken from the Yellow Sea were studied. 9-10 nasal sacs were recognized. They are the paired vestibular, nasefrontal, premaxillary,vomeronasal sacs and the acc-essory sac, the last was single in most specimens, but paired in some specimens. The vestibular sac was very large, its transversal slitlike orifice opened in the anterior wall of nasal passage. The orifices of left and right sacs were connected. The ventral wall of the vestibular sac was thick and throw into 10-15 transversal ridges. No anterior or posterior fold of vestibular sac was found. The anterior portion of the nasofrontal sac was well distended. The pesterior portion was vertical and opened into inferior vestib-ule. The premaxillary sac was small, situated on the bulbous convexity of the premaxi-lla. It seems that much air could hardly be stored in the sac. Accessory sac was very small and generally only the right one present. Neophocaena has also a pair of vomero-nasal sacs which are vertical and behind the posterior portions of nasofrontal sacs. The right nasal sacs were obviously large than the left ones. There were two lip-like struct-ures on each side of the deep part the caudal to the nasal passage-the posterior lip of the nasal passage and the septum between the vomeronasal sac and the posterior portion of the nasofrontal sac. The diagonal membrane was vestigial and no associated muscle fibers were found. So for Neophocaena at least, diagonal membrane may not play an important role in sound production. Two pairs of fatty structures, which Cranford (1986) named dorsal bursae, were found around the nasal passage of Neophocaena. No "museau de singe" was recognized.