392 



HARRIS HAWTIIORXE WILDER ON 



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Port CeT)fov(/^ 



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Fm 



16th vertebra ; ventral aspect. X 3. 



spicuously amphicoelous. In the recent state 

 these depressions are filled in with portions of the 

 original notochord which become restricted to 

 these intervertebral segments by the develop- 

 ment of the osseous vertebrae. Corresponding to 

 the shape of the space included by two approxi- 

 mated ends of vertebrae, these notochordal seg- 

 ments are in tlie shape of two cones placed base 

 to base, the place where the two bases meet being 

 the line of separation between the two vertebrae 

 involved. 



The neural arch is much flattened dorsally, 

 and its sides, the neural laminae, become so much 

 obscured by fusions with the elements of the 

 transverse process that they are seen distinctly 



only when the vertebra is viewed from one end. The main bulk of the arch consists of 

 a flat neural plate, which in a dorsal view of the vertebra nearly conceals the rest. 

 This plate is approximately a rectangle with sides a little incurved. Anteriorly its cor- 

 ners become prolonged into a pair of rounded anterior zygapophyses, and posteriorly it 



develops a pair of somewhat similarly 

 shaped posterior zygapophyses, between 

 which extends a short, median process. 

 As the posterior zygapophyses of each 

 vertebra overlap the anterior ones of 

 the next succeeding, the articvilar sur- 

 faces of the former lie upon the ventral, 

 and those of the latter upon the dorsal 

 aspect. At the blunt posterior point of 

 the posteriorly directed median process, there is a small cup-shaped depression filled, in 

 the recent state, with a nodule of cartilage which forms the tip of the neural spine, the 

 osseous continuation of which extends along the median line of the neural plate, becom- 

 ing obsolete anteriorly. 



The term " transverse process " is a convenient name by which to distinguish certain 

 composite and irregular masses placed upon either side of the centrum and bearing the 

 proximally forked ribs. Each transverse process consists essentially of two cartilnginous 

 rods, dorsal and ventral, encased in an irregular bony mass. Of these two rods, the dor- 

 sal one, the diapophysis, proceeds from the side of the neural arch, while the ventral 



Fig. 3. 16th vertebra ; left lateral aspect. X 4. 



