376 BRITISH FOSSIL REPTILES. 



two diameters of its proximal end, gradually becomes more slender as it descends ; 

 its lower half is trihedral, and stands rather sharply out from the large metapodial (n); 

 its extremity is broken off; the large and small diameters of the lower fractured end 

 are 5 lines and 3 lines. It is not probable that its presence was conspicuous beneath 

 the integument which covered it, but it may have supported a rudimental toe and claw. 



The second metapodial (ib., n) is 8 inches in length, 4^ inches in the longest 

 diameter of the proximal end, 3 inches in that of the distal end. The bone expands 

 at both ends, more suddenly at the distal one ; it is convex on its free or tibial side, 

 flattened on the side next the third metapodial, with the anterior border produced 

 near the middle of the shaft into a process with a convex outline, and with a ridge 

 projecting from the inner and back part of the proximal end. This ridge has been 

 fractured. The outer or fibular angle of the back part of the proximal end is produced 

 towards the next large metapodial, but has likewise been fractured. The articular 

 surface at this end is flat, rather rough, showing vascular pits and other evidence of 

 having been covered, in the recent state, by a layer of fibro-cartilage : by which it was 

 articulated to the innermost tarsal or carpal bone. The distal articular surface is 

 convex from before backwards, slightly convex transversely at its anterior half, with 

 a middle concavity and lateral convexities, transversely, at the posterior half, which is 

 somewhat broader than the fore part of the joint, and with the outer (fibular) angle 

 produced. 



The inner (tibial) side of the distal end of this metapodial has a broad and shallow 

 depression for the attachment of a lateral ligament ; the articular surface is two inches 

 and a half higher than that of the adjoining (third) metapodial, and the proximal end is 

 one inch and a half higher than that of the adjoining bone ; but this is probably due 

 to some dislocation of the metapodial before the matrix hardened around it. 



The third metapodial (ib., m) is 11^ inches in length. The proximal articular 

 surface is slightly convex ; a small portion of its back part is continued upon a thick 

 process from that part of the bone, which rises some way above the level of the hori- 

 zontal surface, apparently about an inch ; but the summit of this process has been 

 broken off. This process subsides as it descends to the inner border of the shaft, 

 about halfway down. 



The inner and anterior angle of the proximal end is produced toward the second 

 metapodial, rendering the side next that bone rather hollowed out, as for its reception 

 when in its proper position. There is no process from the middle of the shaft near its 

 fore part, as in the second metapodial. The distal end expands into a broad trochlear 

 surface, convex from before backwards, concave transversely ; the fore-and-aft extent 

 of the tibial side of this joint is the greatest ; it appears to have been covered by 

 articular cartilage, the extent of the cartilage being well defined by the transverse 

 line at which the smooth surface rises a little above the level of the rough surface 

 for ligamentous attachment. 



