. Outlines of zoology. or coccyx. The first vertebra bears two facets for the two condyles ofthe skull, and an odontoid process which lies between thecondyles. It has no transverse processes, and its arch isincompletely ossified. Each of thenext six has an anteriorly concave orprocoelous centrum, a neural arch sur-rounding the spinal cord, a transverseprocess from each side of the base ofthe arch, an anterior and a posteriorpair of articular processes, and a shortneural spine. The eighth vertebra hasa biconcave or amphicoelous ninth is convex in front, with twoconvex tubercles behi
. Outlines of zoology. or coccyx. The first vertebra bears two facets for the two condyles ofthe skull, and an odontoid process which lies between thecondyles. It has no transverse processes, and its arch isincompletely ossified. Each of thenext six has an anteriorly concave orprocoelous centrum, a neural arch sur-rounding the spinal cord, a transverseprocess from each side of the base ofthe arch, an anterior and a posteriorpair of articular processes, and a shortneural spine. The eighth vertebra hasa biconcave or amphicoelous ninth is convex in front, with twoconvex tubercles behind, and bearslarge • transverse processes with whichthe hip-girdle articulates. The uro-style, formed by the fusion of severalvertebrae, has anteriorly a dorsalarch enclosing a prolongation of thespinal cord; but both arch andnerve-cord soon disappear 313.—Vertebral ^^^ notochord, around which the ? vertebral column has developed, isfinally represented only by the ves-in the centra of the verte-. column and pelvicgirdle of bull-frog. /./., Transverse processes tigesof sacral vertebra: //., . brae, ilium ; U., urostyle ; Fe.,femur ; Isch,, ischiacregion. The skull consists — (a) of thepersistent parts of the original car-tilaginous brain-box or chondrocranium, developed, as inthe skate, from parachordals and trabeculae, plus nasaland auditory capsules ; {b) of ossifications of parts ofthe chondrocranium, cartilage bones ; {c) of membraneor investing bones; and (d) of associated visceral arches Two ex-occipitals bounding the foramen magnum and forming thecondyles, two pro-otics or ossifications of the original auditory capsule, THE AXIAL SKELETON. 583. and an unpaired sphenethmoid forming the front of the brain-case, arecartilage bones. Probably the slendet rods Icnown as quadrato-jugalsor jugals are also cartilage bones. Two parieto-frontals and two nasals above, a paired vomer and anunpaired dagger-shaped parasphenoid beneath, and two lateralhammer-shaped
Size: 1055px × 2369px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
