WEALDEN FORMATIONS. 49 



Wight, and is in the collection of Felix Knyvett, Esq., by whose kind permission it is 

 here described and figured. It has an irregular, slightly concave base, broader than 

 it is high, and has a well-marked deep vascular groove on each side : that to the left, 

 d\ skins into the substance of the bone as it approaches the apex, where it commu- 

 nicates with several large vascular foramina : the right groove, c , resembles that in 

 fig. 2, in being shorter and more curved ; but it seems to have given off its branches 

 to the claw-forming matrix before sinking into the substance of the bone : the upper 

 surface between these grooves is narrower and less convex than the under one, in 

 which respect this phalanx also resembles figs. 1 and 2. Fig. 3 gives a side view, the 

 left, of the second example of straight conical phalanx, showing the narrowest 

 transverse diameter of the bone, as in fig. 1. Fig. 5 is a smaller phalanx of the same 

 unsymmetrical, conical form, with an irregular slightly concave basal articulation, and 

 with impressions of the two lateral vascular grooves; that on the left side, d', being the 

 best marked, and sinking into the substance of the bone, as in the other specimens 

 figured. It is from the Wealden of Battle, Sussex ; and is also in the collection of 

 Felix Knyvett, Esq. 



Having thus, as I believe, determined the true nature of the supposed horn of the 

 Iguanodon, and lowered the problematical fossil from its place on the forehead to the 

 end of one of the toes of some great Wealden Saurian, it remains to inquire to which 

 of the gigantic reptiles of that formation the present phalanx may be, with most 

 probability, referred. 



There are three forms of fossil phalanges from the Wealden strata. One is broad, 

 depressed, subsymmetrical, rounded at the apex, with the outer boundary of each 

 lateral vascular groove produced like two aliform ridges, and the grooves commonly 

 terminating without sinking into the bone. 



This form of phalanx Dr. Mantell to refers the hind foot of the Iguanodon : and 

 that it belongs to the Iguanodon is shown by the instructive series of bones of the 

 same individual, rescued by Mr. Bensted from the Green Sand quarry at Maidstone. 



Another form of phalanx is the reverse of the above, being compressed, curved 

 downwards, with the lateral grooves longer and shallower, and their lower or outer 

 boundary is not produced into an aliform process. This form is figured in the '" Won- 

 ders of Geology,' pi. iii, fig. 1, as belonging to the fore foot of the Iguanodon. 



The ungual phalanges on both the fore and hind feet of the Iguana resemble this 

 second form more than they do the first ; but by no means differ from each other, as 

 those of the Iguanodon must have done on Dr. Mantell's hypothesis. 



In the fore foot of the Crocodile the ungual phalanx of the first toe is broad and 

 depressed, with lateral ridges, and more resembles the phalanx in the Maidstone 

 Iguanodon : the ungual phalanx of the third digit of the Crocodile is of the same length 

 as the first, but is thinner in both transverse and vertical directions, though least in 



