136 REPORT — 1841. 



nizable character superadded, in being bent outwards with a considerable 

 curvature. 



A massive fragment of a broad osseous plate, bearing a segment of a large 

 articular cavity at its thickest margin, and thence extended as a thinner plate, 

 bent with a bold curvature, and terminated by a thick rounded labrum, offers 

 characters of the Lacertian type of the pubis too obvious to be mistaken. 

 This specimen is from .the Tilgate strata; and, since the modifications of the 

 ilium of the Iguanodon in the Maidstone skeleton approximate to the Lacer- 

 tian type of the bone, and especially as manifested by the great Varani, in 

 which the recurved character of the pubic plate is most strongly marked, we 

 may, with much probability, assign the fossil in question to the pelvis of the 

 Iguanodon. 



This fine portion of pubis is of an inequilateral triangular form, 16 inches 

 in its longest diameter, 9 inches 6 lines across its base or broadest part, 



6 inches 8 lines across its narrowest part. The fractured surface of the bone, 

 near the acetabulum, is 3 inches 3 lines thick. The acetabular depression is 



7 inches across, a proportion which corresponds with that of the acetabular 

 concavity in the ilium, and with the size of the cavity in which the head of 

 the Iguanodon's femur must have been received. One, angle of the cavity, 

 corresponding with the anterior one in the Varanus, is raised ; a broad and 

 low obtuse ridge bounds the rest of the free margin of the cavity. The 

 smooth labrum exchanges its character near one of the fractured edges of 

 the bone for a rough surface, which indicates the commencement of the sym- 

 physis. In the apparent absence of the perforation below the acetabular de- 

 pression, the present bone agrees with the Crocodilian type. 



Ischium — A second fragment of a large lamelliform bone (No. ^g, Man- 

 tellian Catalogue) presents, in its general form and slightly twisted character, 

 most resemblance to the ischium, with traceable modifications intermediate 

 to those presented by the extinct Goniopholis and modern Varani and Iguance, 

 The loss of the acetabular extremity, which is broken away, prevents a cer- 

 tain determination of this bone ; the only natural dimension that can be taken 

 is the circumference of the neck, or contracted portion between the acetabu- 

 lar end and the expanded symphysial plate : this circumference gives 7 inches. 

 The slight twist of the bone upon this part as it expands to form the broad 

 symphysial plate, — a character which is well marked in the ischium of the 

 Goniopholis, — gives it a superficial resemblance to the humerus of some of the 

 large Mammalia ; but the bone is too short in proportion to the breadth in- 

 dicated by the fractured symphysial end, to afford a probability of its having 

 been the humerus of a land reptile, and much less of the Iguanodon, in which 

 the form of the femur is well ascertained ; unless, indeed, there be actually 

 more discrepancy between the femur and humerus in size and form in the 

 Dinosaurs, than has, hitherto, been recognized in the Reptilian Class. 



Femur.-^The Maidstone Iguanodon does not satisfactorily determine the 

 question of the principal bone of the fore and hind extremities, for whilst the 

 clavicles, many anterior dorsal vertebrse and anterior ribs, would lead one to 

 suppose that the two long bones found in their proximity might be humeri ; 

 on the other hand the presence of the iliac bones, with some caudal vertebrae 

 in the same slab, give equal probability to their being femora. The bones in 

 question (1 and 2 in the figure of the Maidstone Iguanodon, published by Dr. 

 Mantell in his ' Wonders of Geology,' vol.i. pi. ii.) have the same general cha- 

 racters, viz. the fiattened trochanter at the proximal end, the compressed ridge- 

 like process at the middle, and the two condyles with the deep and narrow 

 fissure at the distal end, which are presented by the larger detached bones, 

 described by Dr. Mantell as femora, from the Tilgate strata. They are other- 



