364 J. W. HULKE ON A MODIFIED 



39. Appendix to " Note on a Modified Foem of Dinosaurian Ilium, 

 hitherto reputed Scapula." By J. W. Hulke, Esq., F.R.S., 

 F.G.S. (Read June 9, 1875.) 



A recent discovery of Iguanodon-rem&ms in the Isle of Wight by 

 the Rev. W. Fox has solved the riddle of the bone which, in the 

 above note, I brought under the Society's notice towards the close 

 of last Session*, and it has also completed our knowledge of the 

 pelvic elements of Mantell's Iguanodon. It will be remembered that 

 Mantell and, later, Owen had regarded the bone as a scapula, first 

 of Iguanodon, and afterwards of some unknown reptile, that this 

 decision seemed to be untenable, and that the balance of all the 

 evidence I could up to that time collect respecting it favoured its 

 being an ilium. 



This fresh material, which Mr. Fox has courteously permitted me 

 to examine, consists of a series of vertebras, of fragments of large flat 

 bones which cannot be any thing else than pieces of the ilia, of a pair 

 of ischia, the former clavicles, and a pair of the bones in question. 



The vertebras comprise the sacrum and a few of the adjoining lumbar 

 and caudal vertebras. Their form, and also that of the ischia, agree 

 so closely with those of the types of Mantell's Iguanodon in the 

 British Museum as to leave no doubt of their generic identity. The 

 third pair of bones in the pelvic girdle, which are neither ilia nor 

 ischia, must be pubes (fig. 1, P). Their shape closely repeats that 

 of the smaller of the two specimens illustrating my note (pi. xxxii. 

 fig. 1, vol. xxx.). Inverting the bone there figured, its long slender 

 process (Spp) is easily identified with the thin elongated rod which, 

 in the Mantell- Bowerbank specimen of the nearly allied Hypsilo- 

 phodon, Prof. Huxley recognized as the pubis (Pb, pi. ii. Quart. 

 Journ. Geol. Soc. vol. xxvi.). This identification roughly gives the 

 direction of the whole bone. Its long slender branch slanted down- 

 wards and backwards parallel to the ischium ; and the little process 

 detached from its posterior surface meeting a corresponding process 

 observable in all well-preserved ischia, converted the upper end of 

 a long narrow obturator-space into a foramen having the position 

 of that which in birds (Ostrich) transmits the tendon of the obtu- 

 rator internus muscle (figs. 1 & 2, obt). The process marked i in 

 the figure (pi. xxxii. vol. xxx.) joined the ilium, and that marked 

 p the ischium ; the smooth intermediate arc formed the lower and 

 front part of the acetabulum, whilst the broad blade-like part sloped 

 ventrally inwards and forwards (figs. 1-3, p). I am inclined to think 

 that the free end of this part met the corresponding extremity of the 

 os pubis of the other side in a median symphysis ; but I have not 

 yet any positive evidence of this in Iguanodon. 



In respect of its large contribution to the acetabulum, the pubis 

 of Mantell's Iguanodon resembles that of existing Lacertilia, as it 

 * Quart. Journ. Geol. Soc. vol. xxx. p. 521, pi. xxxii. 



