1852.] OF THE ROYAL INSTITUTION. 143 
dated by recent discoveries is thus in perfect harmony with the 
remarkable characters which rendered the first known teeth so 
enigmatical : and in the Wealden herbivorous reptile we have a 
solution of the problem, how the integrity of the type of organi- 
zation peculiar to the class of cold-blooded vertebrata was main- 
tained, and yet adapted, by simple modifications, to fulfil the 
conditions required by the economy of a gigantic terrestrial reptile, 
destined to obtain support from vegetable substances: in like man- 
ner as the extinct colossal herbivorous Edentata, which flourished 
in South America, countless ages after the country of the Igua- 
nodon and its inhabitants had been swept from the face of the 
earth. 
The structure of the cervical, dorsal, and caudal vertebrze, of the 
ribs, the pectoral and pelvic arches, the sacrum formed of six anchy- 
losed vertebrz, the bones of the extremities, and certain dermal 
appendages, were successively described, and illustrated by drawings 
and specimens. From the facts adduced Dr. Mantell infers that this 
stupendous reptile equalled in bulk the largest herbivorous mam- 
malia, and was as massive in its proportions; for living exclusively 
on vegetables, the abdominal region must have been greatly de- 
veloped. Its limbs were of proportionate size and strength, to sup- 
port and move so enormous a carcass ; its length, as proved by re- 
cent discoveries, was of crocodilian proportions, for there is no 
doubt that the tail was very long; and the largest Iguanodon 
may have attained a length of from fifty to sixty feet. 
The Hyleosaurus, Megalosaurus, and several other genera of 
reptiles were severally noticed, and reference made to the speci- 
mens in the British Museum. The Pelorosaurus was next described 
somewhat in detail, and the characters of the stupendous humerus, 
or arm-bone, (41 feet long), scapula, clavicle, vertebra, sacrum, 
and pelvis, were pointed out, with the view of illustrating a most 
interesting discovery made but a few days previously by S. H. 
Beckles, Esq. of St. Leonard’s. 
With much labour and skill, Mr. Beckles had succeeded in ex- 
tracting from a block of Wealden sandstone lying on the Sussex coast, 
and which was only visible at low-water, the perfect radius and ulna 
(bones of the fore-arm), and humerus (arm-bone), of a gigantic rep- 
tile, which Dr. Mantell pronounced to be a new species of Pelorosaurus, 
and proposed to name Pelorosaurus Becklesii, The generic identity 
and specific difference between this humerus and that of the Pel. 
Conybeari, which was placed beside it, were pointed out, and the 
remarkable modification of structure presented by the wlna was 
explained. The arm-bone of the P. Conybeari is 54 inches long, the 
corresponding bone of a Gavial or gangetic Crocodile 18 feet long, 
in Dr. Grant’s Museum, is but 114 inches; the humerus discovered 
by Mr. Beckles is 224 inches in length, and the bones of the fore- 
arm are 16 inches long. A portion of the scaly cuirass which 
covered the limbs and is composed of hexagonal plates, was exhibited. 
The Lecturer then took a rapid view of the other reptiles that were 
contemporary with the Iguanodon, enumerating the Pterodactyles or 
