1873.] HTJLKE ANATOMY OF HYPSILOPHODON FOXII. 531 



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. 

 Fig. 1. Outer surface of right ramus of mandible. 



1 a. Its edentulous anterior extremity viewed obliquely from above. 



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. 66, a side view of 6fl. 



7. Two views of a cylindrical tooth. 



8. The pes. a, distal extremity of the tibia. 



Discussion. 

 Prof. Owen remarked that palaeontologists generally were inter- 

 ested in obtaining such additional evidence of the generic charac- 

 ters 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. Pox 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, espe- 

 cially 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 Echino- 

 don 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 Igua- 

 nodon, and supposed to be peculiar thereto, suggested to Prof. 

 Huxley the term Hypsilopliodon. But the lower molars of Iguano- 

 don 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 cha- 

 racter, 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. 



