WEALDEN FORMATIONS. 



39 



Indies. 



Lines 



4 







7 



9 



8 



9 



. 24 







4 



3 



1 



9 



. 13 



6 



It presents the following dimensions : 



Antero-posterior diameter of centriini 



Transverse diameter of centrum 



Vertical diameter of centrum 



Height of vertebra to summit of neural spine* 



Antero-posterior diameter of spine 



Thickness at posterior part of base 



Height of neural spine 



From these dimensions it will be seen that the vertebra of Pelorosaurus is shorter 

 in proportion to its breadth than in the Iguanodon; in that respect resembling 

 Cetiosaurus: the sides of the centrum are more concave lengthwise and less flattened 

 vertically than in the basal tail-vertebrae of Iguanodon. Both the articular ends 

 of the centrum are more deeply cupped. The neural spine is thicker and relatively 

 shorter than in Iguanodon, but much longer than in Cetiosaurus ; whilst the neural 

 canal is more contracted than in either of those genera. 



The anterior caudal vertebrae of Pelorosaurus differ from those of Cetiosaurus 

 in the readily recognisable character of the singleness of the htemapophysial surface 

 (Tab. XI, h), and in this particular they resemble those of Iguanodon. As in the 

 anterior caudals of that genus, also, the surface is much less marked at the fore 

 than at the back part of the centrum. There is no longitudinal fossa connecting 

 them (as in Tab. IX, fig. 5, ' Monograph,' 1855): but this character is not common 

 to all the caudal vertebrse in Iguanodon. 



Humerus. Tab. XII. 



The limb-bone, four feet and a half in length, discovered in 1847 by Mr. Peter 

 Fuller, in the Wealden sandstone of Tilgate Forest, Sussex, so far as its extremities 

 can be judged of in their present mutilated state, bears a closer resemblance to the 

 right humerus of the Crocodiles and Alhgators than to any other long- bone of known 

 Reptilia. But were the wanting parts, of the proximal end more especially, to be 

 such as to cause a closer resemblance to that end of the femur in Iguanodon or 

 Megalosaurus than at present appears, the process d (Tab. XII, fig. 2), which, on 

 the humeral determination, is the deltoid ridge, would answer to the inner trochanter 

 [d), in the femur of the above-named Dinosaurs (see Tab. YII, ' Monograph,' 1856), 

 a process which is wanting in the Crocodilian femur. I incline, however, to 

 believe in the determination of this bone, adopted by the authors of the Memoir on 



* From a contiguous vertebra of similar size, from the same collection and series, equally marked 

 Pelorosaurus, and with the neural spine entire. 



