138 REPORT — 1841. 



ternal walls of this bone are very thick, at least 1 inch. The length of this 

 bone is 27 inches, but. it wants the distal end. The proximal articulation is 

 very convex from behind forwards, but, at the middle, it is slightly concave 

 from side to side. In. Lines. 



Its lateral diameter is 12 



Its antero-posterior diameter is 5 6 



The disparity of size between the tibia and fibula is considerable, but the 

 disparity in the thickness of the two extremities of the bone is less than in the 

 bone which is described and figured as the fibula by Dr. Mantell. On the 

 middle of one of the flat sides of the fibula is an oblong rough surface slightly 

 raised, measuring 3 inches by 2 inches. The articular extremities of the fibula 

 are tuberculate ; the larger end is 4 inches across, the smaller one 3 inches 

 across. The shaft is subcompressed. 



A few yards from the three preceding bones was found the, presumed, hu- 

 merus, which measured 35 inches in length, being very nearly equal in size 

 with the femur. Its proximal extremity is crushed and mutilated : the shaft 

 is compressed from before backwards ; concave behind : the submedian ridge 

 or compressed process is developed from the inner side of the shaft at the usual 

 situation, and corresponds in form with those of the bones Nos. 4 and 5, Man- 

 tellian Collection. The distal condyles are divided anteriorly by a narrow lon- 

 gitudinal furrow, which penetrates deeply between them. As the absence of the 

 deep fissure between the condyles of the femur is repeated in the humerus of 

 the Iguana, so may its presence be repeated in the humerus of the Iguanodon. 



The inner condyle projects backwards beyond the outer one, which is di- 

 stinguished by being traversed by a longitudinal groove. This bone difliers 

 from the femur in the shorter neck supporting the head, in its more promi- 

 nent median process, and in the uniform though slight concavity of the inner 

 margin of the shaft. 



The preceding observations were made during an inspection of the fossils 

 in Mr. Holmes's interesting collection in the summer of 1840. I have subse- 

 quently been favoured by a letter from that gentleman, containing the follow- 

 ing clear and valuable observations on tiie two large bones in his collection, 

 which support the view I had taken of their nature. 



"I have also examined the two large bones concerning which so much 

 doubt exists. They both appear to belong to right extremities, but as the 

 one which has the trochanter, and which by way of distinction I shall call 

 No. 1 (humerus?), is so much crushed in the direction of the rough ridge, so 

 strongly marked in the other, I cannot say with any degree of certainty whe- 

 ther it possessed the same form or not. There is, however, this difference at 

 any rate. The head of No. 1 is so much mutilated that little can be said 

 about it, but it is very clear that the neck is shorter than that of No. 2 (fe- 

 mur?), and there is a variation of nearly one-half in the degree of obliquity 

 from the perpendicular of the shaft of the bone in which the two heads are 

 set on ; that of No. 2 being more so than the other. They also differ in an- 

 other respect. In measuring from the inferior part of the head, supposing 

 both bones to be placed in an erect position, to the superior portion of the 

 condyle, which is the best way in which I can ascertain their relative length ; 

 No. 2 is longer in the shaft than the other bones, which, if they both belonged 

 to the same individual, (and I think there is no sufficient reason to doubt it) 

 would, according to thy conjecture, make it appear that one is the femur and 

 the other the humerus. 



" The question next arises as to which of the bones either name is to be ap- 

 propriated. No. 1 has the trochanter, which is very similar in shape to the 

 femur marked No. 5 in the British Museum. No. 2 has none in its present 



