THE IGUANODON AND HYL^OSAURUS. 
,303 
Unfortunately the bodies of the vertebrae have been crushed and compressed almost 
flat laterally, and the natural form of the inferior part of the centrum is destroyed, 
the visceral aspect presenting a sharp ridge, and thus assuming a different contour 
to that of the adult cervical figured in Plate XXVIII. fig. 1, which has been compressed 
in an opposite direction. Nevertheless, the close analogy between these vertebrae is 
sufficiently obvious ; the structure of the neural arch (as seen in fig. 9“*) is identical ; 
and the only essential difference in the bodies of the respective vertebrae, is that the 
anterior articulating facet (a') is much less prominent in the young specimen than in 
the adult : but as the posterior facet {a") is deeply concave, it is probable that in 
the recent state the anterior facet possessed a cartilaginous convex epiphysis, by which 
the ball-and-socket joint was completed: as in the skeleton of the young Gavial the 
facets of the sacro-coccygeal vertebra are flat, though very convex in the adult*^; 
so in the Iguanodon, the ball and socket of the cervicals may not have been fully 
developed and ossified till the reptile arrived at maturity. 
Fig. A. A concavo-convex dorsal vertebra from Tilgate Forest : natural size. 
I have introduced this figure to prove the existence in the Country of 
the Iguanodon, of small Lizards having the spinal column constructed of 
vertebrae anteriorly concave, and posteriorly convex, as in the living 
Iguanas, Crocodiles, &c. : the very reverse of those above referred to the 
Iguanodon. 
A, is a lateral view ; and A' the anterior aspect, showing the deep socket for the 
reception of the head of the antecedent vertebra. 
PLATE XXX. 
Fig. 10. The right Scapula or Omoplate of the Iguanodon: from Tilgate Forest 
(one- fourth natural size). 
10“. Inner aspect. 
10*. The external aspect. 
a. The upper or spinal end. 
h. The humeral extremity. 
c. The coracoid facet or articulating surface. 
d. The glenoid facet, forming half the cavity for the reception of the 
head of the humerus. 
Fig. 11. The right Coracoid of the Iguanodon; drawn of a size to correspond with 
the scapula. 
s. Scapular facet or surface to articulate with the scapula. 
d'. Glenoid facet, forming with the corresponding part of the scapula, the 
glenoid socket. 
e. Notch for the passage of vessels. 
* See Wonders of Geology, 6th edit. p. 418. 
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