284 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



saurus, in which the coracoid (" Geol. Trans." vol. vi. pi. xliii. 

 fig. 3) is of a more complicated structure than in the Iguano- 

 don and Hylaeosaurus, and somewhat resembles that of the 

 Iguanas or Varanians. 



" I had often vainly attempted to find such a correspond- 

 ence between the articulating facets of the coracoid and 

 scapula above mentioned, as would warrant the conclusion! 

 that they originally belonged to the same genus of saurians. 

 By the fortunate discovery of a perfect Scapula which fulfils 

 these conditions, and can also be shown to belong to the 

 Iguanodon, both the bones forming the scapular arch are now 

 for the first time demonstrated. 



" This specimen is represented l the natural size in 

 'Philos. Trans.' 1849, pi. xxx. fig. 10 ; when obtained it was 

 firmly imbedded in the hard Tilgate sandstone, and broken 

 into several pieces : I succeeded in extricating the whole from 

 the rock, and in reuniting the dissevered parts, so as to demon- 

 strate the perfect form of this most interesting fossil. It is 

 the right scapula, and is 13 inches long, 5^ inches wide at 

 the humeral, and 4 at the upper or spinal extremity ; like 

 that of the Crocodile, it is slender, flat, and slightly arched : 

 at the humeral end it is thick, and expands to form the apo- 

 physial surface that united with the coracoid, and the outer 

 half of the glenoid cavity to receive the head of the humerus . 

 it is flat and thin at the upper or distal end. This bonei 

 differs essentially from the scapula of the Iguanas, Monitors. | 

 &c., and approximates to that of the Crocodiles and Seines : 

 the minute scapula of the Chameleons presents the samej 

 simple characters. 



" Upon placing this Scapula in juxtaposition with the Cora-<! 

 coid above assigned to the Iguanodon, it will be manifest thai 

 the two bones must have belonged to the same scapulai, 

 arch as is shown in Lign, 58. The close resemblance be- i 

 tween this form of pectoral arch and that of the Hylseosaurus ! 

 will be seen at a glance by reference to the latter. The 

 Scapula of the Iguanodon differs from that of the Hylaeosaurus 

 in having the body more arched and slender, and the neck 

 more contracted ; and in the absence of the strong acromial 

 ridge which characterises the latter. The Coracoid differs 

 chiefly in its greater external convexity, and inner conca- 

 vity, and in the apophysial scapular surface being separated 



