. Outlines of zoology. Zoology. THE SKULL. 663 basi-occipital; the median basisphenoid which lodges the pituitary body in a dorsal depression called the sella turcica; the paired alisphenoids fused to the sides of the basisphenoid ; the median presphenoid which forms the lower margin of the optic foramen between the two orbits ; the paired orbitosphenoids, fused to the presphenoid, sutured to the alisphenoids and squamosals, and surrounding the optic foramen ; the vertical pterygoids attached at the junction of basisphenoid and alisphen- oids ; the partly vertical palatines^ united above to th
. Outlines of zoology. Zoology. THE SKULL. 663 basi-occipital; the median basisphenoid which lodges the pituitary body in a dorsal depression called the sella turcica; the paired alisphenoids fused to the sides of the basisphenoid ; the median presphenoid which forms the lower margin of the optic foramen between the two orbits ; the paired orbitosphenoids, fused to the presphenoid, sutured to the alisphenoids and squamosals, and surrounding the optic foramen ; the vertical pterygoids attached at the junction of basisphenoid and alisphen- oids ; the partly vertical palatines^ united above to the presphenoid and behind to \\\^ pterygoids and alisphenoids, separating the posterior nasal passages from the orbits, and uniting in front to form the posterior part of the bony palate ; the median vertical mesethmoid cartilage extending in front of the presphenoid, separating the two nasal cavities, posteriorly ossified and expanded into the sieve- like cribriform plates through the apertures of which the branches of the olfactory nerves pass to the nose ; the paired vomers along the ventral edge of the mesethmoid ; and lastly, the anterior bony palate formed from inward extensions of maxilliB ^nd pre?naxilhc. Wedged in between the occipitals, the squamosals, and the Vjones of the basisphenoid region, there is on each side a periotic bone surround- ing the internal ear. It ossifies from three centres in the cartilaginous auditory capsule, and consists of a dense petrous portion enclosing the essential part of the ear and a more external porous mastoid portion which is produced downwards into a mastoid process in front of the paroccipital process. From each periotic a tympanic bone extends outwards, swollen basally into a tym- panic bulla in which the tympanum or drum of the ear is stretched, and continued around the external audi- tory meatus. From an aperture be- tween the tympanic and the periotic the Eustachian tube passes to the pharynx. Stretching from the tympanum to th
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
