Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/417

1869.J HUXLEY-MEGALOSAURUS. 313 The first tooth is laid bare by the breaking away of the substance of the jaw through its whole length. It measures 6.4 inches in length, 2.6 inches of this length being occupied by the crown, the rest by the fang of the tooth. The fang is an inch wide where it passes beyond the alveolar margin of the jaw. It is nearly straight and seems to have been slightly compressed from side to side. The crown is laterally compressed, slightly curved, and tapers to a point. Its anterior longitudinal contour is convex; the posterior is concave, and formed by a ridge with a serrated free margin. I observed traces of the former contour of a large tooth in the middle of the wide interval between the first and the second tooth.

The second tooth is the biggest of all, and projects for nearly three inches beyond the alveolar margin of the jaw. Of this three inches, 2.7 inches is occupied by the enamelled, pointed, and laterally compressed crown, which is much more curved than that of the first tooth. Where the fang passes under the alveolar margin it is 1.2 in. wide. The circumference of the fang at this point has an ovate contour, the front curve being much flatter than the hinder. The same general character is preserved in the crown for 1.7 inch below the commencement of the enamel; but between this and the apex, the middle line of the anterior face of the crown is raised into a sharp serrated ridge, similar to that which occupies the whole extent of the middle line of the posterior face of the crown, and even, as in the first tooth, extends upwards on the fang, a little beyond the line of the rest of the enamel, before it comes to an end. The crowns of the third and sixth teeth resemble that of the second; those of the fourth and fifth teeth are broken. The three hinder teeth gradually diminish in size, their extra-alveolar lengths and greatest diameter being respectively. IV. V. VI. in. in. in. in. in. in. 2.7 0.9 2.3 0.8 1.75 0.7 The teeth are quite free from the jaw, being merely applied against the outer wall of the alveolar groove, which extends very far beyond the inner; so that the alveolar groove is relatively very short and can only lodge the teeth in the earliest stage of their development.

Note. — The skull of a young Dinosaurian reptile, either identical with or very closely allied to Iguanodon Mantelli, has been discovered by the Rev. W. Fox in the Wealden formation of the Isle of Wright, at Cowleage Chine, and was exhibited, on his behalf, at the Norwich Meeting of the British Association by Mr. Fellows. On that occasion I made some remarks in Section C upon the characters presented by this very interesting specimen; and as Mr. Fox has kindly permitted me to have the fossil for examination, I propose to submit a detailed account of it to the Society on a future occasion. For the present I content myself with observing that the form of the snout is totally different from that exhibited by Megalosaurus. The praemaxilla is produced into a prolongation which seems to have been edentulous, though sharp and conical teeth project from the