146 
DR. MANTELL ON A PORTION OF THE LOWER JAW 
h. Germ of a successional tooth. 
k. The external aspect of the same. 
Fig. 5. Magnified view of a portion of the dental parapet of the fossil, (the space 
marked x, fig. 1,) to exhibit the situation of the germs of the successional 
teeth, h h. 
Fig. 6. Oblique fore-shortened view of figure 1, to show the row of vascular fora- 
mina (/, l, l, /), and the fractured ends of the fangs of the teeth on the 
alveolar margin of the dentary bone a a. 
Fig. 7* The external surface of the right ramus of the lower jaw of an Iguana, fig. 3. 
a. Dentary bone. 
c. Complementary bone. 
d. Surangular bone. 
e. Angular bone. 
f Articular bone. 
Fig. 8. View of the external surface of the fossil, figure 1. 
a a. Alveolar plate of the dentary bone. 
b. Opercular bone. 
i. Canal for the inferior maxillary vessels. 
1 1. Vascular foramina in the dentary bone. 
Fig. 9. Transverse section of the anterior extremity of the fossil, fig. 8. 
PLATE VI. 
Teeth of the Iguanodon and Hylceosaurus (?), of the natural size. 
Figs. 1,2, 3. The most perfect tooth hitherto discovered of a very young Igua- 
nodon, showing the apex slightly worn by use, the serrated lateral mar- 
gins of the crown, the longitudinal ridges, and the curved and tapering 
form of the shank, or fang. 
1. External surface; 2. mesial aspect; 3. lateral view. 
Fig. 4. A tooth of the Iguanodon, with the crown rounded by detrition. 
Fig. 5. The mesial aspect, and fig. 6, the external surface of a tooth of a young 
Iguanodon. 
a. Surface worn obliquely smooth by use. 
b. Fang almost wholly removed by absorption from the growth of a suc- 
cessional tooth. 
Figs. 7, 8. The germ of a successional tooth of an Iguanodon. 
Figs. 9, 10, 11. The tooth of an unknown reptile ; probably referable to the Hylaeo- 
saurus. 
9. The external aspect ; 10. the mesial or inner surface ; 1 1. lateral view. 
