2 
FOSSIL REPTILIA OF THE 
Femur. Tab. I. 
I may premise that the femur of the Iguanodon is characterised by the deep 
and narrow fissure dividing a compressed external trochanter from the head of 
the bone, and by a process from the middle of the shaft, on the inner side, 
opposite to the part where the “ third trochanter ” projects in some of the large 
herbivorous mammals {Perissodactyla). Both these characters are repeated in the 
specimen of the uncompressed shaft of the femur represented in Tab. I ; but the 
shaft, viewed sideways, as in fig. S, shows a more decided sigmoid flexure than in 
the Iguanodon, and the fissure between the great trochanter (e) and the proximal 
end of the bone (c) is relatively deeper. The exterior surface of the shaft is 
smooth, and in the present fossil glistens, and is, as it were, bronzed by a thin 
coating of pyritic salt. The proximal end of the bone (c) divided by the cleft 
from the great trochanter (e) is subcompressed from side to side below the 
swelling out of the head, and is extended from before backwards ; the head itself, 
or articular end of the bone, has been broken or abraded away, showing a fine 
cancellous structure at that part (fig. 3, e). The antero-posterior diameter of this 
part is 6 inches ; the transverse diameter, opposite the base of the outer trochanter, 
is 3 inches 8 lines. 
The fore part of the shaft (fig. 2) shows at its upper half a flattened, oblong, 
rather rough surface (/) for muscular implantation. Below, and on the outer 
side of this surface, is a rough, roundish, slightly prominent tuberosity («), con- 
tinued at its inner side into a ridge, which descends with a slight curve out- 
wards on the fore part of the middle of the shaft of the femur, where it terminates 
in a point at These risings indicate the force of the large muscles acting upon 
the limb, and by their insertions raising and drawing forward the femur. The 
elongated base of the inner process (fig. 3, f) becomes slightly narrower as it 
descends ; its full extent is not recognisable, by reason of the wall of the shaft 
being there broken away, exposing the medullary cavity (m). Behind the base of 
the process is a large, oblong, rough ridge, indicating the extension of the surface 
of attachment, behind and beyond the process itself, for a powerful muscle 
depressing and drawing back the femur. I do not find this character so well 
marked in the femur of the Iguanodon. The homologous roughness is present, 
without the process, in the femur of the Megalosaur. From the great trochanter 
(e) a narrow, rough surface, not projecting as a ridge, extends nearly straight 
down the outer and back part of the shaft (fig. 1 o). Exterior to this surface is 
an oval foramen (a), most probably for the passage of the blood-vessels and nerve 
to the medullary cavity. 
