OF TILGATE FOREST. 
307 
scribed in a former part of this memoir, as appearing 
to constitute a second system, I slioidd be disposed, 
from their number, and from their so commonly 
occurring in the localities where the teeth of the 
Iguanodon most abound, to refer to that animal ; 
it must, however, be mentioned, that the concavo- 
convex vertebra.' which correspond so entirely with 
those of the Iguana, and Monitor, would seem to 
offer a more })robable a])proximation ; yet the ex- 
treme rarity of the latter renders it questionable, 
since there appears no reason why the vertebnn 
should not have been preserved in as considerable 
numbers as the teeth. The chevron bones already 
described as belonging to the second vertebra?, 
serve to add to the probability that they are re- 
ferable to the Iguanodon. 
jRibs. Portions of enormous ribs of a prismatic 
form occur, which must have belonged to the 
skeleton of a colossal reptile, but they present no 
other remarkable character. 
Sternum. A small sternal bone has been dis- 
covered, which corresponds to the sternum of an 
Iguana ; it is represented of its natural size, PI. III. 
fig. 4. 
Clavicles. The clavicles in the Iguana and 
Monitor are very simple, forming a gentle curv- 
ature, which is attached by one extremity to the 
sternum, and by the other to the omoplate ; a 
small bone of this kind has been found, which is 
their true relations were not ascertained until the opportunity was 
afforded me of comparing them with the os tympani of the Moso- 
X 2 
saurus. 
