142 REPORT — 1841. 



the substance of the bone about 1§ inch from its fractured apex. Below one 

 of these canals there is a shallow smooth impression, corresponding no doubt 

 with the margin of the claw. The under surface of the phalanx indicated by 

 the concavity of the curved grooves is more convex transversely than the 

 upper surface : the distance between the converging lateral grooves in this 

 surface is one inch. 



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 the Iguanodon's ungual phalanges are, for the most part, 

 flattened from above downwards. One of these compressed phalanges must 

 have been at least four inches in length ; it now measures three inches, with 

 the extremity broken ofi"; 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 pha- 

 langes, and it 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 resem- 

 ble 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 botli transverse and vertical directions, but is 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.oc?/tos)) is much less than that which is manifested 

 between the depressed and the compressed phalanges hitherto referred to the 

 Iguanodon. 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 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. 



Size of the Iguanodon. — From the comparison, which the few connected 

 portions of the skeleton of the Iguanodon enable us to make, between the 

 bones of the extremities and the vertebral column, it is evident that the hind- 

 legs at least, and probably also the fore-legs, were longer and stronger in pro- 

 portion to the trunk than in any existing Saurian. One can scarcely suppress 

 a feeling of surprise, that this striking characteristic of the Iguanodon, in com- 

 mon with other Dinosauria, should have been, hitherto, overlooked ; since the 

 required evidence is only an associated vertebra and long bone of the same 

 individual, or a comparison of the largest detached vertebrae with the longest 

 femora or humeri. This characteristic is, nevertheless, one of the most im- 

 portant towards a restoration of the extinct reptile, since an approximation to 

 a true conception of the size of the entire animal could only be made after the 

 general proportions of the body to the extremities had been ascertained. 



But it is very obvious tliat the exaggerated resemblances of the Iguanodon 

 to the Iguana have misled the Palaeontologists who have hitherto published 

 the results of their calculations of the size of the Iguanodon; and, hence, the 

 dimensions of 100 feet in length arrived at by a comparison of the teeth and 

 clavicle of the Iguanodon with the Iguana, of 75 feet from a similar compa- 

 rison of their femora, and of 80 feet from that of the claw-bone, which, if 

 founded upon the largest specimen from Horsham, instead of the one com- 



