ROOM III. CHEVRON-BONE OF THE IGUANODON. 275 



nodon to which these vertebrae belonged, must have been at 

 least twenty-seven inches. 



CHEVRON-BOXE, or hcemapophyses. Wall-case C, left-hand 

 shelf, lowest compartment. The form of this element of the 

 caudal region is well shown in this large and perfect specimen, 

 which is figured in my " Fossils of Tilgate Forest," pi. xii. 

 It is eleven inches in length, and 2 inches in antero-posterior 

 diameter. The two laminae of which this bone essentially 

 consists, are in the Iguanodon blended at the proximal end 

 into an expanded cuneiform head, which fits into the corre- 

 sponding intervertebral space left by the truncated angles of 

 two contiguous vertebrae ; and the distal portion constitutes 

 a strong solid spine, a wide interspace, forming the canal for 

 the passage of the large blood-vessels of the tail, being left at 

 the upper part (as is shown in Lign. 35, fig. 2, 3, and 3 a, /, 

 p. 1 64) ; this channel is three inches long in the specimen 

 before us. The blending of the proximal articular ends of 

 the haemapophyses into a single head, is constant throughout 

 the caudal region of the Iguanodon, so far as my knowledge 

 extends ; among the hundreds of caudal vertebrae which I 

 have examined, the unity of the hamapophysial surface is 

 distinctly impressed. 1 



OTHER VERTEBRAE, in Wall-case C. It would extend this 

 article to an undue length were I to dwell on the anato- 

 mical characters of the other vertebrae in this Case, some of 

 which, Dr. Melville and myself believe to be referable to the 

 Iguanodon, while Professor Owen refers them to other genera. 

 On many of these points the evidence appears to me to be in- 

 sufficient to warrant a positive decision ; and it will be most 

 conducive to the successful elucidation of the subject by future 

 inquirers, if, in this place, I subjoin a list of the specimens, 

 with Professor Owen's interpretation of them. 



1 The figure of a caudal vertebra with two distinct hsemapophysial 

 surfaces, in Professor Owen's Monograph on " Cretaceous Fossil Beptiles," 

 PL XXXVII. is certainly not a representation of a normal character : 

 neither is the circular face of the centrum of the dorsal vertebra in 

 PL XXXVI. ; nor the posterior zygapophysis in PL XXXV. In fact, 

 all these parts of the skeleton in the Maidstone specimen are so dis- 

 torted, that it is impossible an artist can give the true characters of the 

 original bones : especially when seen through the glass case that covers 

 them. 



