Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/464

 spine, distant about 1 inch from the bottom of the notch between the praezygapophyses. The posterior opening of the neural canal is much narrower than the anterior : only the upper part of it remains ; its sides form an angle of about 80°.

One of the first questions which arises is, to what region of the spine does this vertebra belong ? In the almost complete absence of the centrum, this question cannot be certainly answered. Its cumbrous size, the great platform, and the restraint which the super-added median bolt and notch impose on the play of the zygapophyses point, I think, to the trunk. Next, the small size and the direction of the articular facet at the end of the transverse process appear ill suited to constitute it the sole and sufficient vertebral support of a rib of dimensions commensurate with those of the vertebra. This makes it likely that there was a capitular costal articular surface on the side of the centrum ; and a double costal vertebral articulation, taken in connexion with the other character, points to the front half of the trunk.

The marked reptilian character of the Wealden fauna favours the presumption that this is also the vertebra of a reptile. Shortly summed, its distinctive features are : —

Textured. — The compactness of the osseous tissue, its occurrence chiefly in thin plates, the thinness of the cortical layer of the bone, and the immense spaces of the cancellous tissue.

Constructive. — 1. The vertical median plate, or bolt, beneath the postzygapophyses, and the corresponding notch between the praezygapophyses.

2. The composite neural spine.

3. The great platform.

4. The buttresses and arches by which the spine, neurapophyses, transverse processes, and platform are strengthened, and the groined interior arch at the front of the neural canal.

The peculiar textural characters enable us readily to separate these from other Wealden bones. My attention was first drawn to these four years ago by Mr. Fox, who had already at that time collected many fragments of this sort from the Wealden cliffs in the neighbourhood of Brighstone, not one of which, however, was sufficiently complete for me to glean an idea from it as to the part of the skeleton from which it had come. The texture of these fragments reminded me more of the coarse diploe of the Elephant's skull than of any thing else with which I was acquainted. They told of the former existence of a large animal distinct from any of the known Dinosaurs, having a skeleton comparable for its lightness with that of Pterosauria, but of a size far surpasing any of these. About a year after this, while examining the Streptospondylian vertebrae in the British Museum, I was struck with the close resemblance, as regards colour and texture, of one of these to the pieces of bone which Mr. Pox had shown me, and the suspicion arose in my my mind that these were portions of this Streptospondylus. I have lately reexamined this vertebra, and find the same textural simila-