| OCR Text |
Show 434 MR. J. W. HULKE ON THE SKELETAL [Nov. 20, With the ascent of the parapophysis on the lateral surface of the centrum, the ventral surface of this becomes narrowed and a low keel arises here at its middle. The terminal surfaces of the centrum have a subcircular outline. In vertebrae referred to the anterior region of the thorax, the centrum assumes a cylindroid form. In a few, in which the parapophysis is passing off the centrum on to the neural arch, the antero-posterior dimension of the centrum is slightly less than in the neck, and in the succeeding vertebrae in the posterior part of the trunk. In these last the centrum is nearly cylindric, contracted at Fig. 3. psz Cervical vertebrae of Steneosaurus. its middle, and dilated at both its ends (fig. 4, p. 435). In the anterior caudal vertebrae the centrum is laterally slightly compressed, its ventral aspect cylindroid. The transverse process in these vertebrae is suturally attached in the level of the neuro-central suture, the sutural impression being shared by the centrum and the neurapophysis. In vertebrae deemed by their smaller size to be situated posteriorly to the above, the centrum is much more compressed laterally, which, with tbe flatness of the under surface, gives the centrum a parallelopipedal figure (fig. 5, p. 435). In these vertebrae the |
