18 PROCEEDINGS OF THI! GEOLOGICAL SOCIETY. [Nov. 10, 
‘4, The head of the femur is set on at right angles to the shaft of 
the bone, so that the axis of the thigh-bone must have been parallel 
with the middle vertical plane of the body, as in birds. 
“<5. The posterior surface of the external condyle of the femur pre- 
sents a strong crest, which passes between the head of the fibula and 
the tibia, as in birds. There is only a rudiment of this structure in 
other reptiles. 
“6, The tibia has a great anterior or ‘ procnemial’ crest, convex 
on the inner, and concave on the outer side. Nothing comparable 
to this exists in other reptiles; but a correspondingly developed crest 
exists in the great majority of birds, especially such as have great 
walking- or swimming-powers. 
“7, The lower extremity of the fibula is much smaller than the 
other ; it is, proportionally, a more slender bone than in other rep- - 
tiles. In birds the distal end of the fibula thins away to a point, 
and it is a still more slender bone. 
“8, Scelidosaurus has four complete toes, but there is a rudiment 
of a fifth metatarsal. The third, or middle, toe is the largest, and the 
metatarsal of the hallux is much smaller at its proximal than at its 
distal end. Iquanodon has three large toes, of which the middle is 
the longest. The slender proximal end of a first metatarsal has 
been found adherent to the inner face of the second, so that if the 
hallux was completely developed it was probably very small. No 
rudiment of the outer toe has been observed. 
“Tt is clear, from the manner in which the three principal meta- 
tarsals articulate together, that they were very intimately and firmly 
united, and that a sufficient base for the support of the body was 
afforded by the spreading out of the phalangeal regions of the toes. 
“From the great difference in size between the fore and hind 
limbs, Mantell and, more recently, Leidy have concluded that the 
Dinosauria(at least Iguanodon and Hadrosaurus) may have supported 
themselves for a longer or shorter period upon their hind legs. But 
the discovery made in the Weald by Mr. Beckles, of traces of large, 
three-toed foot-prints, of such a size and at such a distance apart 
that it is difficult to believe they can have been made by any thing 
but an Jguanodon, lead to the supposition that this vast reptile, and 
perhaps others of its family, must have walked, temporarily, or per- 
manently, upon its hind legs. 
“« However this may be, there can be no doubt that the hind quar- 
ters of the Dinosauria wonderfully approached those of birds in 
their general structure, and, therefore, that these extinct reptiles 
were more closely allied to birds than any which now live’’*. 
There is one part of the organization of the Dinosawria which is 
not mentioned in this enunciation, because I did not at that time 
see its bearing upon the problem under discussion, I mean the very 
singular structure of the distal moiety of the tibia. 
It took me a great deal of trouble to comprehend the structure of 
_ * Proceedings of the Royal Institution of Great Britain. Friday, Feb. 7, 
1868. 
