1869.J HUXLEY MEGALOSATJRUS. 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 con- 

 cave, 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 com- 

 pressed 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 Kttle 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 dimi- 

 nish 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. 



Wote. — The skull of a young Dinosaurian reptile, either identical 

 with or very closely allied to Iguanodon Mantelli, has been dis- 

 covered by the Rev. W. Fox in the Wealden formation of the Isle of 

 V^ight, at Cowleage Chine, and was exhibited, on his behalf, at the 

 Norwich Meeting of the British Association by Mr. Pellows. On 

 that occasion I made some remarks in Section C upon the characters 

 presented by this very interesting specimen ; and as Mr. Pox 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. 

 Por the present I content myself with observing that the form of the 

 snout is totally difi^erent 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 



