ROOM III. SACRUM OF THE IGUAXODON. 269 



contiguous bones ; the foramina for the transmission of the 

 sacral nerves from the spinal chord, being situated above and 

 behind the middle of the bodies. 



Fragments of the pelvic arch, consisting of the centrum 

 of one vertebra, with portions of others anchylosed to the 

 articular ends, are not uncommon; and so long since as 

 1826, Sir Roderick Murchison transmitted to Baron Cuvier 

 a specimen of this kind, found at Loxwood in Sussex, 1 with 

 several lumbar and caudal vertebrae. Upon these bones 

 M. Cuvier remarked, that the united bodies of the ver- 

 tebrae "seem to indicate that the animal to which they 

 belonged made such feeble use of its tail that the caudal 

 vertebrae were occasionally anchylosed together." 2 Even the 

 magnificent specimen of the sacrum of the Megalosaurus, 

 consisting of a series of five united vertebrae, figured and 

 described by Dr. Buckland, in 1824, did not suggest the true 

 structure of this part of the skeleton. The announcement of 

 this fact was therefore to me of special interest, since it eluci- 

 dated the nature of several fossils in my collection that were 

 previously unintelligible. 



With the view of acquiring an accurate idea of the vertebrae 

 composing the sacrum of the Iguanodon, I obtained Mr. 

 Saull's permission to have his unique and most instructive 

 specimen completely developed at my own expense, as its 

 characters were in some measure obscured by a layer of hard 

 calcareous grit, with which, as is generally the case in the 

 Isle of Wight Wealden bones, it was partially encrusted. 3 



This Fossil was obtained from the Wealden beds in Sandown 

 Bay, and is strongly impregnated with oxide of iron, and 

 traversed by veins of calcareous spar. It is the sacrum of 

 a young animal, and consists of six anchylosed vertebrae (not 



1 " Geological Transactions," vol. ii. (New Series), p. 105, Plate XV. 

 figs. 4, 6. 



2 On Baron Cuvier's last visit to England, in 1 830, 1 showed him some 

 vertebrae anchylosed in like manner, and on which he made the same 

 remark. 



3 The specimen is figured (for the first time) in PL XXVI. of my 

 "Memoir on the Iguanodon, Phil. Trans." 1849. As Mr. Saull, with 

 great liberality, throws his museum open to visitors every Thursday 

 after mid-day, this unique fossil can be seen by any person interested in 

 this department of Palaeontology. 



