200 
DR. MANTELL ON THE IGUANODON. 
Fig. II. Outline of the under or inferior aspect of the same. 
1. 1. Area for the attachment of the protractor muscles of the tongue, 
e, e. The mental tubercle. 
Fig. III. Section presented by the posterior fractured end of the specimen (see Plate 
XVI. fig. 2) ; reduced half linear. 
l, 1. The outer wall or parapet of the alveolar process. 
2. Remains of the inner or mesial alveolar parapet. 
3. Posterior section of the great dental canal ; the lesser foramen indicates 
the channel for the vessels sent off from the main trunk to supply the 
dental germs. 
4. The opercular furrow. 
Fig. IV. The external aspect of the specimen represented in Plate XVI., reduced one- 
half in linear dimensions. In this view the numerous vascular foramina 
leading from the dental canal are distinctly shown ; they extend in a line 
parallel with the alveolar margin, and are continued to the anterior ex- 
tremity of the symphysis ; one large foramen being situated immediately 
under the mental tubercle (e). 
e. The mental tubercle forming the anterior extremity of the symphysis. 
fi. A fracture on the side of the bone, by which the course of the great 
dental canal is exposed to view. 
i. An eminence at the commencement of the anterior edentulous portion of 
the jaw. 
J{. A deep groove beneath the margin of the symphysis. 
m. The coronoid process. 
PLATE XVIII. 
Teeth of the Iguanodon. 
Fig. 1. A molar tooth belonging to the left side of the upper jaw, having the crown 
worn by use : from Tilgate Forest. 
1. The outer or external aspect, showing the ridged and enamelled surface 
of the crown. 
1“. Lateral view of the tooth. 
F. Surface of the crown worn smooth by mastication, and presenting two 
distinct facets (1 and 2), produced by the attrition of the corresponding 
lower molars. 
f. The fang. 
n. Marks the primary ridge. 
Fig. 2. Upper molar of the left side, in which the crown of the tooth is much abraded 
