‘ 
Ww) 
b 
2 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 10, 
previously considered to be a femur, he found that it was really the 
distal end of the tibia, corresponding in all its broad features with 
Cuvier’s specimen from the Honfleur clays. Deslongchamps’s very 
just appreciation of the close affinity between his Pockiloplewron 
and Megalosaurus would haye been immensely fortified if he had 
been acquainted with the true structure of the distal end of the tibia 
of the latter reptile. 
I had got thus far in February 1868, and it was on the strength 
of the facts just mentioned that I included Potkiloplewron in the 
list of the Dinosauria, in the lecture which has been cited. At that 
time, however, I had not seen the following notes by Prof. EK. D. 
Cope, of Philadelphia, which are contained in the ‘ Proceedings of 
the Academy of Natural Sciences of Philadelphia,’ for November 
1866 and December 1867, and in the ‘ Proceedings of the Boston 
Natural History Society’ for June 1869, and which constitute im- 
portant additions to his previously published account of the Ameri- 
can Megalosauroid Lelaps. 
The similarity of Prof. Cope’s general conclusions to my own, in 
his second note, render it necessary for me to point out that I could 
not possibly have known anything about them when my lecture 
was delivered, still less at the time when the letter from Prof. 
Phillips which I have cited, was written. 
“HK. D. Cope pointed out the anomalous relations existing be- 
tween the tibia and the fibula in certain of the Dinosauria, as 
illustrated by the genus Zwlaps. He remarked, the distal extre- 
mity of the tibia is transverse and much compressed, and does not 
exhibit any of the usual appearances of an articular surface, neither 
the reptilian condyle, nor a cotyloid cavity sufficient for an astra- 
galus of the size necessary for an animal of such bulk. A bone 
presenting a broad hour-glass-faced articular surface was disco- 
vered with the other remains, and had puzzled the anatomists who 
had seen it. This piece exhibits along its whole posterior aspect 
two faces, which form a reentrant angle for a fixed articulation ; 
this is found to have been applied to the extremity of the tibia 
exactly, and to have been fixed by strong articular ligaments. 
The medianly constricted condyle, presenting forwards and a little 
downwards, exhibits so little analogy with the astragalus, as to 
suggest other interpretations; and after a careful examination, it 
seems evidently the distal extremity of the fibula. This element 
furnishes a small articular surface at the knee, and fitting the tibia 
by the concavity of its inner face, becomes greatly attenuated at its 
distal third, where it is, in consequence of the obliquity of its 
direction, applied to the anterior face of the former bone. It then 
spreads into a plate extending to the inner margin of the tibia, 
while the solid shank is continued along the outer margin, and both 
terminate in the massive condyle, which embraces the whole extre- 
inity of the tibia, like an epiphysis. 
“One other example only of this structure is known in the Ver- 
tebrata, of which I only find mention in Cuvier, ‘ Ossemens Fossiles,’ 
