DR. MANTELL ON THE IGUANODON. 
199 
the Hylaeosaurus. I therefore propose to distinguish this fossil Saurian by a name 
indicative of the district from which, in common with so many relics of the same 
class, it was obtained — Regnosaurus * ; with the specific appellation of Northamptoni, 
as a tribute of respect to the eminent nobleman whose approaching retirement from 
the Presidency of the Royal Society is so much to be regretted, 
19 Chester Square, Pimlico, 
May 24, 1848. 
Description of the Plates. 
PLATE XVI. 
A considerable portion of the right ramus of the lower jaw of an adult Iguanodon 
from the Wealden sandstone of Tilgate Forest, discovered by Capt. Lambart Brick- 
enden, F.G.S. The figures are of the size of the original. 
Fig. I. The inner or mesial aspect. 
a. The coronal germ of the first anterior tooth, in its alveolus. 
h. The crown of a successional tooth in its natural situation. 
c. Portion of the base of a successional tooth. The above are visible in con- 
sequence of the removal of the inner parapet of the alveolar process. 
d, d. The deep elongated opercular furrow, originally covered by the splenial 
or opercular bone. 
e. An obtuse tubercle or projection forming the anterior termination of the 
symphysial portion of the jaw. 
f, f,f Denote some of the alveoli or sockets of the mature molar teeth. 
m. The coronoid or complementary bone. 
s. The articulating surface forming the symphysial suture. 
Fig. II. An oblique external view of the same specimen. In this figure the coronoid 
process (m of fig. 1) is not delineated, and the fractured posterior end of 
the fossil is represented to show the situation of the great dental canal {g), 
and the thickness of the parietes of the bone ; the internal course of this 
canal is exposed by the fracture {h). 
PLATE XVII. 
Fig. I. Outline of the anterior part of the lower jaw of the Iguanodon, seen from 
above ; reduced one-half the natural size in linear dimensions. 
s, s. The symphysial suture. 
e, e. The mental tubercle. 
* Sussex Saurian ; the County of Sussex was anciently inhabited by the Regni, 
