WEALDEN DINOSAURS. 365 



the Wealden matrix. The shape of the outer ( iv) and inner ( n ) of these bones indi- 

 cates that three alone constituted their segment of the foot, unless some styliform 

 rudiment may have existed, which has left no mark of junction with the next fully 

 developed metapodial* bone. 



Those bones of the foot of the Iguanodon, described in pp. 373 — 378, and figured in 

 Pis. 43 and 44, afford a means of comparison with the present specimen, and show 

 that it cannot belong to the corresponding foot of the Iguanodon, and that it is very 

 improbable that it can belong to another (fore or hind) foot of the same species. It 

 plainly indicates a foot of longer and more slender proportions, with a different 

 configuration of the metapodial bones. The relative lengths of these bones show 

 that they belong to a foot of the same side of the body as that of the Iguanodon above 

 described. 



The proximal ends of the three bones have been broken off obliquely, the outer- 

 most (PI. 42, ii) retaining the greatest proportion of the shaft : the innermost (ib., iy) 

 retains its distal articular surface ; the middle bone (ib., m) has a portion of the same 

 surface. The distal end of the outermost bone is broken away. 



By the analogy of the metapodium of the Iguanodon, the innermost metapodial 

 of the present specimen answers to the second in the pentadactyle foot, the middle to 

 the third, and the outermost to the fourth. The foot to which they belonged was 

 functionally tridactyle, through the arrest of development or suppression of the first 

 and fifth toes in the pentadactyle foot. 



The metapodial ( n) has a sub-compressed shaft, convex on the inner or free side 

 (figs. 1 and 2), slightly concave towards the middle metapodial ; with the anterior 

 margin sharp, but not produced at the middle of the bone, as in the Iguanodon : 

 the distal articular surface is convex at its anterior half, trochlear at its posterior half, 

 or with a median, rather oblique groove between two tuberosities. 



The middle metapodial (m) differs from that of the Iguanodon in its uniformly 

 almost flat anterior surface. The outer metapodial (figs. 1 and 3, iv) has a flatter 

 and relatively broader outer surface than in the Iguanodon : the antero-internal border 

 subsides about half way down the shaft : the internal border appears to be produced 

 towards the middle metapodial, as in the Iguanodon. The distal end of the outer meta- 

 podial ( iv) must have extended lower than that of the inner one. 



The size and texture of the above-described bones of the foot accord best with the 

 characters of the osseous te.xture in the Hyteosaurus, of which they are probably part 

 of the hind-foot. 



* The term "metapodium" signifies the same segment in both fore- and hind-feet, and is requisite in 

 treating of such segment when it cannot be determined whether it is of the fore-foot (metacarpus), or of the 

 hind- foot (metatarsus). 



