310 BRITISH FOSSIL REPTILES. 



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, now in the 

 British Museum, (No. ^, Mantellian Catalogue), is from the Tilgate strata ; and since 

 the modifications of the ilium of the Iguanodon in the Maidstone skeleton approximate 

 to the Lacertian type of the bone, and especially as manifested by the great Farani 

 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 oi Jie Iguanodon. 



This fine portion of pubis is of an inequilateral triangular form, 1 6 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 acetabidar depression is 7 inches across, a proportion 

 which corresponds well 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 commence- 

 ment of the symphysis. In the apparent absence of the perforation below the 

 acetabular depression, the present bone agrees with the crocodilian type. 



Ischium. — A second fragment of a large lamelliform bone, also in the British 

 Museum, (No. ^'i, Mantellian 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 the modern Varani and 

 Iguana. The loss of the acetabular extremity, which is broken away, prevents a 

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

 the circumference of the neck, or contracted portion between the acetabular 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 large Mammalia; but the bone is too short in 

 proportion to the breadth indicated by the fractured symphysial end, to afford any 

 probability of its having been a humerus of a land reptile, and much less of the 

 Iguanodon, in which the form of the humerus is now well ascertained. 



"■a^ 



Femur of the Iguanodon. PL 20, figs. 1, la and \h. One fourth the nat. size. 



Several specimens of this remarkable bone, — the one that most impresses the observer 

 withthe magnitude of theextinct reptileto which it belonged, — are preserved in the British 

 Museum. Of these the most entire and perfect specimen, the subject of tlie above plate 



