184 
DR. MANTELL ON THE IGUANODON. 
that the fossil might belong to the Hyleeosaurus, or to some other genus of reptiles 
whose bones oceur in the Wealden deposits. 
The specimen to which I now solicit attention consists of nearly the entire dentary 
and coronoid bones of the right side of the lower jaw of an adult animal, retaining 
two successional teeth in place, and the germ of a third, with the alveoli or sockets 
of seventeen or eighteen mature molars. This fossil is the first indisputable portion 
of a jaw of the Iguanodon hitherto brought to light ; although nearly a quarter of a 
century has elapsed since the publication in the Philosophical Transactions* of my 
first memoir on the teeth of this extinct reptile. 
From the striking analogy presented by the worn teeth of the Iguanodon to the 
condition of the abraded molars in some of the large herbivorous Mammalia, the dis- 
covery of the maxillary organs of this reptile was an object of the highest palaeonto- 
logical interest, in order to determine in vvhat manner the mastication of vegetables 
was effected by an animal belonging to a class, in which no living species is provided 
with jaws so constructed as to be capable of a triturating or grinding motion ; nor 
with cheeks to retain the food while such a process is performed'!'. And though from 
the absence of mature teeth in the sockets, and of the articular portion of the jaw, 
the proximal end being destroyed, the specimen before us does not afford a complete 
solution of the problem, yet it possesses characters sufficiently definite and intelligible 
to throw important light on the structure and functions of the dental organs of the 
Iguanodon ; and it has also enabled me to ascertain the form of the upper jaw, from 
a portion of the left maxillary bone, collected many years since, and now in the 
Britisli Museum, but whose peculiar characters I was previously unable satisfactorily 
to interpret. 
Before entering upon the description of the highly interesting fossil which forms 
the principal subject of this memoir, I beg to express my most grateful acknowledg- 
ments to Captain Lambart Brickenden, of Warminglid, Sussex, by whom it was 
discovered, and skilfully extricated from the sandstone in which it was imbedded ; 
and who, although I was personally unknown to him, in the true spirit of an ardent 
and liberal promoter of science, placed it at my disposal, as the original investigator 
of the fossil Saurians of the Wealden ; a tribute of respect that I regard as a high 
reward for my humble efforts to advance those branches of natural knowledge, to 
which I have devoted the leisure moments of a life of professional toil. 
The specimen when discovered was imbedded in a block of the fawn-coloured sand- 
stone which occurs interstratified with beds of clay and limestone, throughout a con- 
siderable part of the Wealden districts of the south-east of England ; fortunately this 
stone is not very compact, so that organic remains can be extricated from it by a skilful 
manipulator, with but little difficulty. This fossil, like most of the bones and teeth 
* “ Notice on the Iguanodon, a newly discovered Fossil Reptile, from the Sandstone of Tilgate Forest, in 
Sussex.” — Philosophical Transactions for 1825. 
t See Cuvier, Oss. Foss, tome v. p. 351. 
