140 REPORT — 1841. 



fourth its length : yet the femur of the Iguanodon equals the united length of 

 eleven of its dorsal vertebrae, while that of the Iguana equals the united length 

 of only six of its dorsal vertebrae. 



The femora of the Iguana stand out, like those of most other Lacertians, 

 at right angles with the vertical plane of the trunk, which is rather slung upon 

 than supported by those bones : but it is evident from the superior relative 

 length and strength of those bones in the Iguanodon, from the different con- 

 formation of the articular, especially the proximal extremities, and from the 

 ridges and processes indicative of the powerful muscles inserted into the bone, 

 that it must have sustained the weight of the body in a manner more nearly 

 resembling that in the pachydermal Mammalia. As in some of the more 

 bulky of these quadrupeds, the indication of the 'ligamentum teres 'is wanting 

 in the head of the femur of the Iguanodon. 



The tibia of the Iguanodon equals the united length of nine of the dorsal 

 vertebrae, while in the Iguana it does not exceed the united length of five dor- 

 sal vertebrae, although it more nearly equals the femur in length than in the 

 Iguanodon. The head of the tibia is more expanded and complicated by deep 

 and wide grooves in the Iguanodon : the fibula is less expanded towards the 

 distal end and less flattened against the tibia in the Iguanodon. 



The fibula of the small Iguanodon from the pit at Rusper, equals the an- 

 tero-posterior extent of the spines of eight dorsal vertebrae of the same indi- 

 vidual. This bone is 13 inches long, 2 inches across the proximal end, and 

 6 lines across the distal end. 



Of the great Iguanodon from the Horsham quarry two metacarpal or me- 

 tatarsal bones are preserved in natural juxtaposition : one exceeds the other 

 by four inches, and measures 2 feet 6 inches ; the breadth of its distal end is 3 

 inches 3 lines ; the shaft is compressed and subtrihedral ; its texture is spongy 

 at the centre. The proximal end is expanded, with a nearly flat articular sur- 

 face, the contour of which is broken by two longitudinal indentations : the 

 distal end offers a well-sculptured trochlear articulation for the first phalanx. 

 The bone of the Maidstone-^Ma«oc?ow(marked 7inthe figure above cited in the 

 ' Wonders of Geology') corresponds with the above described bones of the foot. 



Some of the phalanges, probably the middle ones, appear to have been sin- 

 gularly abbreviated ; but they have not yet been discovered in such juxtapo- 

 sition with undoubted Iguanodon's bones as to justify a more precise descrip- 

 tion of their characters under the present head. 



The distal or ungual phalanges of the Iguanodon, although doubtless offer- 

 ing certain modifications of form in different toes, are shown by those pre- 

 served in the Maidstone Iguanodon, and others of much larger dimensions, 

 found associated with the bones of the great Iguanodon of the Horsham 

 quarry, to have had a less incurved, broader and more depressed form than 

 in other known Saurians. Two of the largest ungual phalanges of the Hor- 

 sham Ig^ianodon in Mr. Holmes's collection, are broad, subdepressed, with 

 the curved vascular groove on each side, as in most other Saurians, with a 

 slightly concave articular base, and terminating forwards in a round blunt 

 edge ; the outer boundary of the lateral grooves forms, at the posterior end of 

 the groove, a laterally projecting process, rendering this part of the phalanx 

 broader than the articular extremity or basis. The following are dimensions 

 of the largest of the two phalanges : — In. Lines. 



Length 5 4 



Breadth 3 2 



Breadth at articular end 3 



Depth at articular end 2 3 



The last dimension gradually diminishes to the distal end. 



