. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. Fig. C. — Left tympano-periotic of the exist- ing Delphinapterus leucas Pallas. Inner or cerebral face, inverted, x !• for the nervus facialis is confluent with the porus acusticus on that side of the periotic which is turned away from the tympanic, but it sometimes happens, as in Mesoplodon, that these openings are separated. The nervus facialis emerges on that side of the periotic which is turned toward the tympanic through a small round aperture (apertura tym- panica canalis Fallopiae) which is continued b
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. Fig. C. — Left tympano-periotic of the exist- ing Delphinapterus leucas Pallas. Inner or cerebral face, inverted, x !• for the nervus facialis is confluent with the porus acusticus on that side of the periotic which is turned away from the tympanic, but it sometimes happens, as in Mesoplodon, that these openings are separated. The nervus facialis emerges on that side of the periotic which is turned toward the tympanic through a small round aperture (apertura tym- panica canalis Fallopiae) which is continued backward in the form of a semi-enclosed canal (20). Two other openings are visible on the cerebral face of the periotic, placed one above the other in close proximity to the porus acusticus. The smaller of these communicates directly with the cochlear labyrinth, and is only separated from the ex- ternal opening of the latter (fenestra cochleae) by a slight bridge. The name given to this smaller opening is apertura externa aquaeductus cochleae (14). The larger one above it is called from its communication with the scala vestibuli the apertura externa aquaeductus vestibuli (13). All of these openings vary more or less in form, size, and position amongst differ- ent genera, and hence require attentive exam- ination. Inferior face (Fig. D). — Rotation through an- other quadrant of arc brings into view the lower surface of the bulla ossea. It is trav- ersed longitudinally along its middle portion by a broad sulcus that gradually deepens posteriorly, thus forming an inner (16) and an outer (1) lip. The surface of the latter is smooth, that of the former very rough, the rugosity extending about half-way 19. --// Fig. D. — Left tympano-periotic of the existing Del- phinapterus leucas Pallas. Inferior face, x {.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrat
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