1869. | HUXLEY—DINOSAURIA AND BIRDS. 21 
The determination of the true form of the distal end of the tibia 
of Megalosaurus had some interesting consequences. 
In the ‘ Ossemens Fossiles’ (éd. 4™¢, t. 1x. p. 204, “ Sauriens Fos- 
siles ”’), the following passage occurs :— 
‘A lower portion of a tibia from Honfleur, with the astragalus, 
another bone of the tarsus, and a fragment which possibly belongs 
to the fibula indicate a hind foot of very extraordinary structure. 
«To understand its nature, it is necessary to conceive that the 
leg to which these bones belonged was much compressed from side 
to side, so as to be sharp behind, like the tursus of a duck, instead of 
being flattened from before backwards, like that of the Crocodiles, 
and still more that of the Monitors. Bearing this conception in 
mind, the bone aa, figs. 34-36, has some similarity in form to the 
astragalus of the Crocodile ; but one sees that the caleaneum must 
have been altogether posterior and very small. 
“The articular face of the tibia is 0-14 metre long; its greatest 
width (0:04) is towards its anterior fourth, which is acutely angu- 
lated; posteriorly, the inner edge is undulated. A curved crest ascends 
obliquely along the inner face of the tibia, and articulates with the 
ascending and compressed process of the astragalus. In conse- 
quence of its compression, the form of this astragalus is so curious 
that it mght be taken, at first sight, for the caleaneum of a mammal. 
<¢ Below, it presents a convex cylindrical surface ; above, it is irre- 
gularly concave, to adjust itself to the sinuosities of the articular 
face of the tibia; from its inner edge, posteriorly, arises the com- 
pressed process of which I have spoken. The internal face is semi- 
lunar. Behind, it is truncated, presenting a little concave facet, 
which undoubtedly articulated with the calcaneum. 
«‘The animal to which this lower part of a leg and this tarsus 
belonged cannot have been less than thirty-six feet long, supposing 
it to have nearly the same proportions as the Gavials. If it had the 
proportions of a Monitor, its length must have amounted to forty-six 
feet.” 
Now, on comparing the distal end of the tibia of Megalosaurus 
with that of Cuvier’s Honfleur Saurian, it was quite obvious that 
the two were closely analogous, and that Megalosaurus must have 
had an astragalus very like that of the Honfleur reptile. Evidence 
confirmatory of this conclusion was derived from another quarter. 
The ‘ Mémoires de la Société Linnéenne de Normandie’ (tome vi. 
1838) contain a very remarkable paper by M. Eudes Deslong- 
champs, “ Sur le Poikilopleuron Bucklandit, grand Saurien Fossile 
intermédiaire entre les Crocodiles et les Lézards,” discovered in 
a Caen-stone quarry. The remains of this animal indicate that 
it had a length of from 25 to 30 feet; and as teeth of Megalosawrus 
-Bucklandi occur in the Caen stone, Deslongchamps is inclined to 
suspect that Potkilopleuron may be identical with Megalosaurus. 
Among the bones of his Potkilopleuron, Deslongchamps obtained 
two astragali, the resemblance of which to the bone described by. 
Cuvier in the ‘ Ossemens Fossiles,’ was exceedingly striking ; and 
applying one of these bones to the end of a fragment which he had 
