WEALDEN FORMATIONS. 13 



A distal phalanx (ib., iv, 4), of the same character as that of the second toe, is longer in 

 proportion to its breadth, and deeper ancono-thenally. The rough, obtuse termination is 

 bounded below by a transverse groove indicative of an ungual callosity of a more definite 

 form. 



The fifth metacarpal of the right fore-foot (PI, III, v, m, reversed) has been preserved. 

 Its proximal surface is rather lozenge-shaped ; the transverse diameter is 2 inches 3 lines ; a 

 circular, slightly concave, roughish articular surface is defined at the middle of the lozenge ; 

 the rougher tuberosities, extending beyond it on each side, form the truncate angles of the 

 lozenge in that direction ; a smaller extent of rough surface defines, in a feebler degree, the 

 angles in the opposite direction. The length of this metacarpal is 1 inch 7 lines ; the breadth 

 of the distal end is 1 inch 8 lines. The upper surface is smooth, broad, and almost flat. 

 The radial surface is continued into the thenal one, which is strongly concave lengthwise, 

 and these combined surfaces are roughened by longitudinal ridges and grooves. 



The ulnar surface slopes in that direction strongly from the upper one to meet the 

 combined theno-radial surfaces ; the distal articular surface is trapezoid in form, convex 

 vertically, slightly concave transversely at its middle part, and continued upon a pair of 

 tuberosities thenally ; the toe which it supported would be directed obliquely to the ulnar 

 side of the foot. 



The skeleton of the fore-paw of the Iguanodon, carpus inclusive, may be set down as 

 about 16 inches in length, and about 11 inches in extreme breadth, showing a like dis- 

 proportion of size to the hind-foot which the humerus does to the femur. 



In the Supplement, 1 No. 1, to the ' Monograph on the Fossil Reptilia of the Wealden 

 and Purbeck Formations,' I remarked, in regard to its subject, " the resemblance to the 

 hind-foot of the Crocodilia in the suppression of the fifth toe, and the resemblance of the 

 third and fourth toes, in regard to their nearly equal length, to those toes in the Monitor, 

 render it most probable that the tridactyle foot of the Iguanodon, here described, is a 

 ' hind-foot ;' but it cannot be assumed that the fore-foot may not have been similarly 

 modified." 



We have now the desired evidence, and know that the fore-foot was pentadactyle, and 

 that its chief speciality is in the stunted character of the terminal phalanges, at least of 

 the second and third digits. The entire length of the bony framework of the fore-foot, 

 without the carpus, is 1 foot 1 inch ; its breadth across the proximal ends of the meta- 

 carpals is 9 inches : the length of the bony framework of the hind-foot, without the 

 tarsus, is 1 foot 8 inches ; its breadth across the proximal ends of the metatarsals is 

 9 inches. 



The fore-foot is smaller in proportion to the hind-foot in the Crocodile ; it is still 

 smaller in the Iguana. 



The length of the bony framework of the hind-foot in a Crocodilus biporcatus, with a 



1 Vol. of the Palsecmtographical Society, 4to, for 1858, p. 3. 



