EXPLANATION OF PLATE XVIII.
All the figures, except those of the teeth, are of the natural size. The size of the teeth is indicated on the plate by lines.
2. a, scapula; b, its humeral articular surface; c, coracoid; d, humerus; e, its proximal articular head.
3. Manus. a, b, claw-bones.
4. A perfect tooth of the smaller compressed form.
5. Two worn teeth of this kind, upon which lies a young tooth.
6 and 6a. Two of the larger compressed teeth. 6b, a side view of 6a.
7. Two views of a cylindrical tooth.
8. The pes. a, distal extremity of the tibia.
Discussion.
Prof. Owen remarked that palæontologists generally were interested in obtaining such additional evidence of the generic characters of Iguanodon as Mr. Fox's valuable discovery of the skull and other remains of the small species in the Isle of Wight Wealden might supply; but such desirable information, especially as regards the cranial structure of the herbivorous Dinosaurs, is shut out if those remains are shown to belong to a distinct genus. In the paper to that end in the 'Quarterly Journal' for 1870, p. 3, the only teeth of the so-called Hypsilophodon known to the writer were those of the upper jaw, and these were not entire; the portion of crown answering to the serrated portion in Iguanodon was worn away. Mr. Fox was therefore justified in rejecting Prof. Huxley's genus Hypsilophodon, although he might believe the statement that such serrations were characteristic of the teeth of Iguanodon, especially when emphasized by the phrase "so characteristic"—the fact being, however, that marginal serrations characterize the apical half of the crown in the Dinosaurian genera Scelidosaurus and Echinodon as in Iguanodon. What are truly characteristic of the upper molars of that herbivorous Dinosaurian are the ridges on the outer surface of the crown, which ridges, being also present in Pox's Iguanodon, and supposed to be peculiar thereto, suggested to Prof. Huxley the term Hypsilopliodon. But the lower molars of Iguanodon are equally ridged, but on the opposite side to those above, viz. the inner side; and the marginal serrations extend nearer to the base of the crown. Now the lower molars of the small Iguanodon, also found, with the mandible, by Mr. Fox, show this generic character, and vindicate the taxonomy of their discoverer. We may rest assured, therefore, that the sloping edentulous symphysial part of the mandible of the great Iguanodon had a downbent edentulous part of the premaxillaries applied to it, such as the fore part of the skull of Iguanodon Foxii exhibits. Without a knowledge of the
of the Lias. A stout median ridge is depicted going from the retiring angle of the cingulum to the apex of the crown, which I fail to find: to me it appears that a transverse section of the crown would have its outer contour a simple unbroken curve, having its maximum excursion at the middle line of the outer surface, but uninterrupted here by any angle or bend marking the cross cut of a ridge.
