ROOM III. CAUDAL VERTEBRA OF THE HYKEOSAURUS. 325 



long, and parts of two others anchylosed together, with por- 

 tions of the transposed neural arches. These vertebrae are 

 more elongated than in the Iguanodon, and have the visceral 

 aspect slightly furrowed. This fossil is minutely described 

 in the work referred to. 



But I have recently obtained a much finer specimen of this 

 part of the skeleton of the Hylaeosaurus, if, as I believe, Prof. 

 Owen's determination of the fossil above described be cor- 

 rect. It consists of the bodies of four anchylosed sacral vertebrae, 

 with portions of the haemapophyses, and the medullary canal 

 well defined. It was obtained by my friend Captain Lambart 

 Brickenden, from the quarry in which the first known example 

 of this saurian was discovered. 1 



As neither of the bones in this fossil appears to be a termi- 

 nal one, it is probable that the sacrum of the Hylaeosaurus, 

 like that of the Iguanodon, consisted of six vertebrae. In the 

 complete anchylosis of the bodies of the vertebrae, the position 

 of the sacral ribs and neural laminae, and the slightly sul- 

 cated visceral aspect of the bodies, it entirely accords with 

 the fragment of a sacrum in the Case before us. 



CAUDAL VERTEBRAE OF THE HYL.EOSAURUS. The structure of 

 the caudal portion of the spine of this remarkable saurian is 

 admirably shown in the fine series of twenty-six vertebrae 

 from Tilgate Forest (ante, p. 323). This chain of bones com- 

 prises the base of the tail, and extends to a length of six feet ; 

 and though broken into three portions, and somewhat dis- 

 placed, and the intermediate parts wanting, exhibits the 

 various modifications of the vertebrae, and corresponding 

 chevron-bones, which characterise the caudal region of the 

 Hylaeosaurus. 



The anterior caudals are 2J inches in length, and have 

 remarkably long and thick transverse processes, which pro- 

 ceed from the neural arch, and extend outwards and slightly 

 forwards ; the width of the tail at this part must have been 

 from twelve to fourteen inches. A longitudinal furrow tra- 

 verses the visceral aspect of these vertebrae, and is terminated 

 at each end by two tubercles for articulation with the cor- 

 responding chevron bone, which is about five inches hi length, 



1 This fossil is figured and described in " Philos. Trans." 1849, PI. 

 XXVII. p. 301. 



