WEALDEN FORMATIONS. 35 



The most interesting and instructive information regarding the humerus of the 

 Iguanodon, afforded by Mr. Holmes's discovery, in 1 847, of that bone, associated with 

 the scapula and coracoid, in the same block of stone, was its relative dimensions to the 

 scapula and other bones of the skeleton. The bones, so discovered, are represented, two 

 thirds of their natural size, in Tab. XIV. Being shorter than the scapula of the same 

 individual, and much shorter than the femur, the proportions of the humerus in the 

 Iguanodon resemble more those of the extinct marine crocodile, called Teleosautus, than 

 those of any modern crocodile or lizard, and they indicate, as I have observed in a 

 former Monograph, in connexion with the long, compressed, and vertically extended 

 tail, the aquatic habits of this gigantic herbivorous reptile. 



The head of the humerus, Tab. XIV, fig. 4, a, is somewhat prominent, and projects 

 inwards and backwards at right angles to the shaft, between two sub-equal tube- 

 rosities. From the external of these tuberosities, b, a deltoid ridge is continued 

 nearly half way down the bone, and gives the greatest breadth to the shaft a little 

 above its middle part, at c. Where it subsides, the shaft is bent a little inwards, 

 becomes more rounded, contracts in diameter, and then gradually expands to the 

 distal condyles, d, d. These are rounded and moderately prominent ; the shaft above 

 them offers a broad and shallow concavity anteriorly, fig. 5, and a moderately deep 

 longitudinal depression behind, fig. 3, which is continued into that between them 

 shown at fig. 6. In the length of the deltoid ridge the humerus of the Iguanodon 

 approaches nearer to the form of that bone in the Crocodile than in the Iguana ; but 

 it resembles more the humerus of the Iguana in the degree of concavity of the fore 

 part of the shaft above the condyles. 



The radius and ulna, well shown in the Maidstone Iguanodon, in the British 

 Museum, and figured in Tabs. XXXIII and XXXIV, of the ' Monograph on Cretaceous 

 Reptiles,' offer few differences worthy of notice, except their greater relative strength, 

 from the corresponding bones in the Iguana. The olecranon of the ulna is more 

 prominent and is rounded, as in the great monitor [Varanus niloticus). 



Pelvis and Pelvic or Hinder Extremities. 



The pelvis consists, as in recent reptiles, of the sacrum, with a pair of iliac, ischial, 

 and pubic bones. The iliac bones, which would seem to become anchylosed to the 

 sacrum in old individuals, have been already described, and are represented in 

 Tabs. Ill, IV, and V of the present Monograph, and in Tabs. XXXIII and XXXIV 

 of the ' Monograph on Cretaceous Reptiles.' 



Pubis. — This bone, which presents a simple spatulate form in the Crocodile, already 

 begins to increase in breadth at its symphysial extremity in the extinct family with 

 concave vertebrae ; and in the larger existing species of lizards is expanded at both 

 extremities, and has a very marked and recognisable character superadded, in being 

 bent outwards with a considerable curvature. 



