280 
DR. MANTELL ON THE OSTEOLOGY OF 
Bones of the Extremities. 
Humerus of the Iguanodon, Plate XXXI. — It may be worth remarking', that although 
numerous femora, tibiae, and other bones of the hinder extremities were discovered 
in various localities, no certain remains of the fore-legs had occurred except the 
slender bones described by me as metacarpals*. Professor OwEN'f' suggested that 
some of the bones in the British Museum, which I had considered as femora, might 
possibly be humeri, and the observations of a correspondent are quoted by him in 
corroboration of this opinion ; but I feel confident that no one who will give suf- 
ficient attention to the subject, can for a moment admit the validity of the reasons 
adduced. The question however is now decided by the discovery of a bone found 
in the Wealden of the Isle of Wight, associated with other remains of the Iguanodon ; 
and which is undoubtedly a humerus, because it cannot possibly be referred to any 
other part of the skeleton, and possesses all the essential characters of the principal 
bone of the anterior extremity of a gigantic reptile. Most fortunately, too, it can be 
proved to belong to the Iguanodon ; for it is identical with a well-preserved, but 
much smaller bone, in the Maidstone specimen (Plate XXXI. fig. 20). 
In my memoir of 1841, this last bone is figured:]:, with the remark that “it pro- 
bably belongs to the brachial extremity ; it is imbedded near the two metacarpals, 
but I have not been able to determine its character satisfactorily.” The relatively 
very small size of this bone appeared to be an insuperable objection to the regarding 
it as the humerus, and it therefore seemed to me more probable that it was one of the 
bones of the fore-arm, possibly the radius. In the Reports on British Fossil Reptiles 
it is stated that this bone corresponds with certain bones of the foot found at 
Horsham ; but both the extremities of the fossil in question entirely differ from the 
articulating surfaces of all the metacarpals and metatarsals of the Iguanodon that 
have come under my observation. The comparison of this specimen with the humerus 
from the Isle of Wight will at once establish its true relations. 
The humerus from the Isle of Wight was discovered by Mr. Fowlstone, to whom 
I am indebted for the loan of it; it is figured ^th the natural size, in Plate XXXI. 
fig. 19; fig. 19“ representing the posterior, and fig. 19* the anterior aspect. This 
fine bone is entire, with the exception of the outer tuberosity of the head ; its dimen- 
sions are as follow : — 
Greatest length . 3 feet. 
Length in a straight line from the inner tubercle of the head to] i • i 
the inner condyle J 
sophical Transactions, 1841, Plate IX. fig. 10, must therefore be referred to some other genus of the Wealden 
reptiles ; it may possibly belong to the Megalosaurus, in which the coracoid (Geol. Trans., vol. vi. pi. 43, fig. 3) 
is of a more complicated structure than in the Iguanodon and Hylaeosaurus, and somewhat resembles that of 
the Iguanas or Varanians. 
* Philosophical Transactions, 1841, Plate VIII. fig. 14. 
t Reports on British Fossil Reptiles, 1841, p. 138. 
X Philosophical Transactions, Plate VIII. fig. 5. § Page 140. 
