PROCEEDINGS OF SOCIETIES. 271 



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 

 grange 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 f 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 6ft. 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 



2o % 



