44 FOSSIL REPTILIA OF THE 



belonged to the Iguanodon. The outer boundary of each lateral vascular groove 

 expands to form similar aliform projections, as at b, fig. 2 ; the grooves termi- 

 nate rather abruptly, but do not penetrate the substance of the bone. The upper 

 surface, between the lateral grooves, is convex and smooth; the under surface, 

 shown in the figure, is rough, and impressed by irregular vascular grooves and 

 foramina. In its size and proportions this phalanx agrees with the proximal one 

 figured in the same plate, Tab. XVI, fig. 1 ; it may have belonged to the same indi- 

 vidual, and certainly came from an Iguanodon of the same colossal proportions. 



Among the few other phalangeal bones from Dr. Mantell's collection in the British 

 Museum, there is one (figured in the 'Wonders of Geology,' pi. iii, fig. 1, as belonging 

 to the fore-foot of the Iguanodon) which differs in a marked manner from the 

 specimens just described, being as much compressed from side to side as some of the 

 unquestionably Iguanodon's ungual phalanges are flattened from above downwards. 

 One of these compressed phalanges must have been at least 4 inches in length ; it 

 now measures 3 inches, with the extremity broken off; it is 2 inches 8 lines in vertical 

 diameter at the base, and only 1 inch 2 lines in the greatest transverse diameter. 

 The phalanx is more curved downwards than any of the true Iguanodon's phalanges, 

 and is traversed by a longer and shallower groove, the lower margin of which is not 

 produced into a lateral aliform process, nor does the distal end of the groove sink into 

 the substance of the bone. The ungual phalanges on both the fore and hind feet of 

 the Iguana resemble this phalanx in form more than they do those of the Iguanodon. 

 In the fore-foot of the crocodile the ungual phalanx of the first or innermost toe is 

 broad and flat, with lateral ridges, much resembling the depressed phalanges of the 

 Iguanodon. The ungual phalanx of the third digit is of the same length, but is 

 thinner in both transverse and vertical directions, though less so in the latter ; it is 

 not more curved. Still the difference, and this is the greatest that I can perceive in 

 comparing the different ungual phalanges of the same individual crocodile {Croc, 

 acutus), is much less than that which is manifested between the depressed and the 

 compressed phalanges hitherto referred to the Iguanodon. It is highly probable that 

 the terminal phalanges of the different toes of the Iguanodon were somewhat varied in 

 form ; but the compressed incurved phalanx supposed to characterise the fore-foot of 

 that great herbivorous reptile, appears to me to present rather the form of the phalanx 

 of a great carnivorous Saurian. In the great proportion of the skeleton found near 

 Maidstone are two phalanges which correspond in form with those enormous 

 specimens found near Horsham, and on the south coast of the Isle of Wight, and with 

 the small depressed claw-bones from Tilgate Forest, unquestionably belonging to the 

 Iguanodon, and supposed by Dr. Mantell to be peculiar to the hind foot of that Saurian. 



Amongst the varieties of large fossil ungual phalanges discovered in the Wealden 

 of Kent, Sussex, and the Isle of Wight, I should be more disposed to refer to a 



