ON BRITISH FOSSIL REPTILES. 137 



wise too much crushed and buried to yield materials for more minute com- 

 parison : each of these bones measures 33 inches in length. 



In five separate long bones, having the general characters of the two above- 

 mentioned in the Maidstone Iguanodon, numbered consecutively and marked 

 * Femur' in the Mantellian Collection, Nos. 1 and 3 differ from Nos. 4 and 5 in 

 the greater inward production of the head, making the concavity of the line 

 descending from the head to the median internal ridge somewhat deeper. The 

 lower angle of this median ridge is more produced in Nos. 1, 2 and 3, than in 

 Nos. 4 and 5. The whole inner contour is more regularly concave in No. 5, 

 than in Nos. 1 or 3. Of these five bones, No. 2 was found associated with a 

 tibia and fibula ; and if, therefore, the differences above indicated should be 

 more than mere individual varieties of the same bone, we might conclude 

 Nos. 4 and 5 to be humeri. Such conclusion appears more probable from the 

 circumstance of two of the longest and largest of the bones, having the gene- 

 ral characters of the femur of the Iguanodon, which were obtained by Mr. 

 Holmes from the quarry of the Wealden stone at Horsham, belonging both to 

 the right side. 



Now the other bones obtained in proximity with the above were all parts 

 of one large individual, and it is much more probable, therefore, that we have 

 here a right humerus and femur of the same individual, than two right femora 

 of different individuals. One of the differences noticed in the Tilgate speci- 

 mens, viz. the degree of obliquity at which the neck joins the shaft, is dis- 

 cernible in these ; and close to that bone, which shows the characters that we 

 have supposed to belong to the femur, were found bones corresponding with 

 the tibia and fibula. 



Regarding then this as the femur, it presents the following characters : — it 

 measures 3 feet in length : its circumference at the middle of the shaft is 18 

 inches: the contour of the rounded inward-projecting part of head is 17^ 

 inches : two flat longitudinal facets meet near the middle of the anterior sur- 

 face of the shaft at a rough and slightly elevated angle, which runs straight 

 down to within thirteen inches of the distal end : the ridge there inclines to- 

 wards the internal condyle and subsides. Two strong vasti intermts et ex- 

 ternus muscles are indicated by this ridge. The head of the bone is carried 

 inwards, overhanging the shaft in a greater degree than the corresponding 

 part does in the humerus. The line of the inner side of the shaft describes 

 a graceful sinuous curve, being first concave, then slightly convex at the 

 middle, where there is an indication of the projecting ridge which has been 

 broken off: below this it is concave to the flattened antero-posteriorly ex- 

 tended, slightly concave surface, which descends vertically to the articular 

 surface of the condyle, which surface proceeds horizontally at nearly a right 

 angle with the line of the shaft of the bone. The antero-posterior extent of 

 the flattened condyle is 8 inches. The thickness of the external wall of the 

 shaft varies from half an inch to an inch. 



Both ends of this fine bone are crushed and mutilated. 



By the side of the femur were found two other bones, the largest of which 

 corresponds with the tibia. The external part of the head is considerably pro- 

 duced horizontally; the circumference of the proximal articular surface is 30 

 inches. The longitudinally finely striated vertical surface of the shaft of the 

 bone commences at the anterior part of the proximal end along a well-defined 

 curved line, which runs transversely across the bone, convex downwards in 

 the middle and concave downwards at each end : the bone rapidly contracts, 

 and assumes, about 8 inches below the head, the subquadrilateral form ; it is 

 broadest from side to side: its circumference is here 15 inches. The anterior 

 surface is flattened ; the outer or radial side convex or rounded : the dense ex- 



