134 REPORT — 1S41. 



the undoubted scapula of the Hylaeosaur, and with that of certain Lacertians, 

 especially of the genus Sciticus*, in the production of a long and slender 

 pointed process, continued at nearly right angles with the body of the bone, 

 from the anterior part of the articular surface for the coracoid ; but it differs 

 from the scapula of the Hylasosaur in the presence of two short processes 

 given off from the lower part of the base of the long process, and in the ab- 

 sence of the thick and strong transverse acromial ridge which overarches the 

 glenoid depression, and in the deeper concavity of the posterior margin of 

 the ascending plate or body of the bone, 'i'his part, in its shape, relative 

 length and breadth, is intermediate between the Crocodilian and Lacertian 

 type of the scapula, at least as exemplified in the Monitors and Iguanas, where 

 it is broad and short. The Seines and Chameleons, in the more Crocodilian 

 proportions of their scapulae, resemble the Hylaeosaur and the great species 

 of extinct Saurian, most probably the Iguanodon, to which the present bone 

 belongs. 



Coracoid. — The thick articular portion of this bone, with its characteristic 

 perforation, here continued to the articular margin by a narrow fissure, di- 

 viding the scapular from the humeral articulation, ha^ been found of different 

 sizes in the Tilgate strata, and has been, with much probability, likewise re- 

 ferred to the Iguanodiiii. One of these portions of coracoid, which measured 

 10 inches in diameter, was found in the same block of stone with other 

 unequivocal remains of Iguanodon. 



Clavicle. — The doubts which are attached to the determination of the pre- 

 vious parts of the scapular arch are fortunately dissipated from the considera- 

 tion of this bone by the preservation of both the right and left clavicles in 

 the Maidstone Iguanodon. The presence of the fibula in the same block of 

 stone, and its discovery in close proximity with the tibia and femur in the 

 Wealden strata, satisfactorily prove that the present remarkable bone cannot 

 have formed part of the hinder extremity. And since, in other reptiles, the 

 radius differs from the fibula in little more than in being somewhat shorter 

 and thicker, there is still less reason for supposing it to belong to the fore-arm. 



The form of the ribs of the Iguanodon is well known, and they become 

 shorter and more curved as they advance from the middle to the anterior part 

 of the chest. The determination, therefore, which Dr. Mantell regarded as 

 most probable t, must be held to be the true one. The largest entire clavicle 

 from the Wealden strata measures 29 inches in length, and there is a portion 

 of another in the same collection one-third larger. The largest fibula of the 

 Iguanodon that has been found measures 28 inches. The bone is compressed, 

 slender, and subtrihedral at the middle part, expanded and flattened at the two 

 extremities, bent with a slight double curve in a graceful sigmoid form. The 

 broadest end, which, from the analogy of the Cyclodus lizard, must be re- 

 garded as the median or pectoral extremity, gives off two processes, the first 

 appearing as a continuation of the thinner margin of the bone, twisted and 

 produced obliquely downwards ; the second process is given off nearer the 

 expanded sternal end, towards which it slightly curves. 



* Dr. Mantell has pointed out this resemblance in his Memoir in the Phil. Trans., 1841. 



t " If we consider the form of this hone, it appears that the only place it can hold in the 

 skeleton must be either the thorax or lower extremities ; it may be a iibula, a rib, or a cla- 

 vicle; and that it is a clavdcle of some extraordinary extinct reptile is certainly most pro- 

 bable." — Geology of the South-east of England, p. 309. The subsequent discovery of the 

 Maidstone Iguanodon determined the species of reptile to which the bone in question be- 

 longed, and the comparisons mentioned in the text prove it to be a clavicle. The bone 

 attacl»ed to the coracoid and oraoplate of a small lizard, which I pointed out to Dr. Mantell 

 as resembling the one in question, was the clavicle of the Cyclodus nigroluteus. See Dr. 

 Mantell's late Memoir of 1?41, Phil. Trans., p. 138. 



