142 NOTICES OF THE MEETINGS [March 5, 
small as those of the mouse, while those of the Iguanodon are 
often one inch wide, and three inches in length. Specimens ex- 
hibiting the above characters are however, rare; the summit 
of the crown is usually more or less worn away by use, and 
the fang removed by absorption from the pressure induced by the 
upward growth of the successional teeth. In the first example 
discovered by Dr. Mantell (in 1820), the crown was ground down 
so as to present on its inner face a smooth oblique surface with 
a cutting edge on the summit, and the marginal crenations 
were worn away; in this state the fossil so strikingly resembled 
an upper tooth of a Rhinoceros, that Baron Cuvier pronounced it to 
belong to a species of that genus. Numerous teeth in different 
stages of growth and detrition were at length obtained, and the rep- 
tilian character of the animal to which they belonged was satisfac- 
torily determined. Three years since, the first specimen of the lower 
jaw was discovered by Captain Lambart Brickenden, in the same 
quarry in Tilgate Forest from which the earliest known tooth was 
obtained; and subsequently a portion of the upper jaw with teeth, 
has been procured from the Hastings’ strata. 
Referring to his various Memoirs on the Iguanodon in the Phi- 
losophical Transactions, and to his recent work on the Organic 
Remains in the British Museum,* for details, the Lecturer stated, 
that while the compound structure of the lower jaw, and the 
mode of dentition, established the reptilian character of the ori- 
ginal animal, the maxillary organs presented a nearer approach 
to those of certain mammalia, than is observable in any other 
reptiles. The teeth in the upper and lower jaw were arranged 
in a sub-alternate order as in ruminants; the face of the crown, 
or that having the thickest coat of enamel, is placed mesially 
or on the inner side of the lower teeth, and on the external sur- 
face of the upper. The anterior part of the lower jaw is eden- 
tulous, and its symphysial extremity forms a scoop-like process, 
which resembles the corresponding part of the inferior jaw of the 
Edentate mammalia, as for example the Mylodons: and the great 
number and size of the vascular foramina of the jaw indicate a 
greater development of the lips, and integuments, than occurs in 
any existing animals of the class Reptilia; the sharp ridge bor- 
dering the deep groove of the symphysis, in which there are 
likewise several foramina for the exit of nerves and blood-vessels, 
evidently gave attachment to the muscles and integuments of the 
lip: while two deep pits for the insertion of the protractor 
muscles of the tongue, manifest the mobility and power of that 
organ, There are therefore strong reasons for supposing that the 
lips in the Iguanodon were flexible, and in conjunction with the 
long fleshy prehensile tongue, were the chief instruments for 
seizing and cropping the leaves, branches, and fruit, which from 
the construction of the teeth we may infer constituted the food of 
the original. The mechanism of the maxillary organs as eluci- 
* “ Petrifactions and their Teachings, or a Hand-book to the Gallery of Organic 
Remains of the British Museum,” one vol. 1851, published by H. G. Bohn. 
