282 
DR. MANTELL ON THE OSTEOLOGY OF 
is about 20 inches, that of the contiguous femur 33 inches; but as the latter is 
somewhat flattened and extended by compression, the difference is probably not more 
than one-third. The Isle of Wight humerus is 3 feet long ; the largest femur I 
have seen is 4 feet 8 inches ; the average size of the femur in the adult was probably 
about 4 feet ; this bone therefore presents the same proportionate length as the 
Maidstone humerus. 
Hinder extremities . — The femur, tibia, fibula, metatarsals, phalangeals,and ungueals, 
have long since been discovered and determined* * * § ; but the bones of the tarsus as 
well as of the carpus are still unknown. I should have passed over these parts of the 
skeleton without remark, but that some of the femora, tibiae, &c. which I have 
recently obtained are of such enormous proportions, as to require notice in proof of 
the colossal size which some individuals must have attained. 
In the course of last autumn I procured from the cliffs near Brook Point, — a locality 
well known to the British geologist from the fossil forest exposed at its base-f, — por- 
tions of two corresponding femora, tibiae, and several vertebrae, fragments of ribs, &c. 
of Iguanodons. The most entire bone is the left femur; it consists of the shaft from 
above the popliteal space to the root of the outer trochanter : the head and condyles 
are both wanting; the inner trochanter remains; the length of this fossil is 3 feet; 
circumference of the shaft 27 inches. The greatest thickness of the wall of the shaft 
is 2 inches; the diameter of the medullary cavity 5 inches by 3 ; in. all the femora 
which I have examined the medullary canal extends from above the condyles to 
within one-third of the top of the bone§. Of the right femur, which from its corre- 
spondence in size is probably referable to the same individual as the left, two large 
portions of the shaft were alone obtained. Now if we take as a scale of proportions 
one of the large femora in the British Museum, the bone above described, if perfect. 
would give the following admeasurements : — 
Total length 4 feet 8 inches. 
Circumference of the head exclusive of the outer trochanter . . . 3 — 2 
the shaft at the base of the middle trochanter . 2 — 1 
the distal end round the condyles 3 — 6 
One of the tibiee found with the above, consists of about two-thirds of the shaft, 
with the distal or tarsal extremity nearly entire : the following are its dimen- 
sions : — 
* Philosophical Transactions, 1841, Plate VIII. 
t See my “ Geological Excursions round the Isle of Wight,” p. 277. 
I Philosophical Transactions, 1841, Plate VIII. fig. 1, for an outline of the perfect form of the femur of the 
Iguanodon. 
§ In this enormous bone the internal structure is beautifully preserved ; sections properly prepared exhibit 
the peculiar form and proportions which Mr. Bowehbank considers to be characteristic of the reptilian type. 
That eminent microscopic observer has kindly favoured me with his measurements of the bone-cells in portions 
of this femur. The general average of the proportions of the length and diameter of the cells is as one to eleven 
and a quarter ; the length being and the diameter sV^th of an inch. 
