278 
DR. MANTELL ON THE OSTEOLOGY OF 
be seen that the clavicles of the Iguanodon were recognized from two of these 
bones occurring in the Maidstone specimen ; and that a coracoid bone, 10 inches 
wide, was also ascribed to the same reptile*, from several examples having 
been found with undoubted bones of the Iguanodon : but the latter reference was 
only provisional, since there was no connecting link to unite this element to the 
other parts of the pectoral arch. A scapula, 18 inches long-j-, for a similar reason 
was placed in the same category ; but with the precautionary remark, “ that neither 
of the specimens was found in natural apposition or connexion with other portions 
of the skeleton, but only imbedded in the same mass of rock.” I have often vainly 
attempted to find such a correspondence between the articulating facets of the cora- 
coid and scapula above mentioned, as would warrant the conclusion that they origi- 
nally belonged to the same genus of Saurians. By the fortunate discovery of a perfect 
scapula (Plate XXX. fig. 10) which fulfils these conditions, and can also be proved to 
belong to the Iguanodon, both the bones forming the shoulder-joint are now for the 
first time determined. 
This specimen is delineated one-fourth the natural size in Plate 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 demonstrate 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 becomes thick and expanded to form 
the apophysial 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 very thin at the upper or 
spinal end. This bone differs essentially from the scapula of the Iguanas, Monitors, 
&c,, and approximates to that of the Crocodiles and Scinks ; the minute scapula of 
the Chameleons presents the same simple character. 
Upon placing this scapula in juxtaposition with a coracoid of the form assigned to 
the Iguanodon it will be manifest that the two bones must have belonged to the 
same scapular arch ; as is shown in Plate XXX. figs. 10 and 11. The close resem- 
blance between this form of pectoral arch and that of the Hyleeosaurus will be seen 
at a glance by reference to the figures of 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 
characterizes the latter. The coracoid (Plate XXX. fig. 1 1) differs chiefly in its greater 
external convexity and inner concavity, and in the apophysial scapular surface 
being separated from the glenoid facet by a deep notch (Plate XXX. fig. lie) for the 
passage of vessels, instead of having a simple perforation as in the Hylaeosaurus. In 
both these reptiles, however, there is a closer affinity in the structure of the pectoral 
arch, than I have observed between other extinct forms. 
* Philosophical Transactions, 1841, Plate IX. fig. 11. p. 138. 
X Ibid. Plate IX. fig. 11. 
t Ibid. Plate IX. fig. 10. 
§ Ibid. Plate X. fig. 8. 
