PROCEEDINGS OF SOCIETIES. 
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in the wonderful development of its neck, having in this region of the spine no 
less than thirty-five bones, being one-third more than is found in any other living 
or extinct animal. This enormous neck, which resembled the body of a Serpent, 
was capable of being flexed into the elegant S-shaped curvature so beautifully 
shown in our Swans: the paddles of this reptile were between the Cetaceous 
character of the preceding genus and those of existing Lizards, and supply us 
with interesting links in the series of organic forms. The spine is arranged with 
a view to give greater solidity to this region of the body, and the tail is extremely 
short, affording a striking contrast to that of the Ichthyosaurus. From the 
solidity of the articulations of the spine, the length of the neck, the shortness of 
the tail, and the development of the extremities, the Plesiosaurus is supposed to 
have frequented shallow seas and estuaries, from being incapable of braving the 
open main. 
The Mosasaurus was described, and its affinities to the Monitors demonstrated; 
in reviewing the history of the marine Saurians, the lecturer observed, that the 
Carnivorous reptiles were the ruling despots of the ocean, during the periods the 
oolitiferous sea rolled its wilderness of waves over our present continents, before 
whose power of speed, whose weapons of destruction, and whose cunning and 
predaceous habits, all the tenants of the deep, when brought within their grasp, 
were alike constrained to yield. 
But the dry land, as well as the waters of those middle ages, was tenanted by 
strange gigantic forms of the same class, organized for subsisting upon a vegetable 
regimen. The lecturer described the enormous terrestrial herbivorous reptile dis¬ 
covered by Mr. Mantell, in the Wealden beds, which he called the Iguanodon , 
from the circumstance of its teeth resembling those of our modern Iguanas. This 
wonderful reptile was supposed by that gentleman to have attained the enormous 
length of seventy feet , and the proportion of its several parts, obtained by a 
rigorous comparison between the volume and dimensions of the fossil bones and 
teeth with those of the Iguanas of our day, were as follows :— 
Iguanadon—the length. 70ft. Oin. 
Length of the head.,.. 4ft. 6in. 
Length of the body * . 13ft. 6in. 
Length of the tail .. 52ft. Oin. 
Height from the ground.. 9ft. Oin. 
Circumference of the body. 14ft. 6in. 
Length of the thigh and leg . 8ft. 2in. 
Circumference of ditto .. 7ft. 6in, 
Length of the hind foot. Oft. 2in. 
The lecturer here compared the dental formula of the Iguana with that of the 
Iguanodon, and stated that the teeth of the latter appeared to be but magnified 
2 o 2 
