684 



PROF. H. G. SEELEY ON THE REPTILE 



vated and expands laterally — though, from the fractured state of the 

 specimen, it is impossible to state the width across the vertebra, 

 which, as preserved, is only 5 centim., but may perhaps have been 

 somewhat more. The centrum appears to have been depressed, as 

 usual in the sacral region, but there is no fracture showing its exact 

 thickness. This form of vertebra is very different from that referred 

 to Iguanodon by Prof. Owen (Pal. Soc. 1854, pi. 3), in which the base 

 of the centrum is a sharp ridge. It is also unlike, but nearer to, the 

 centrum represented by the same author, pi. 7, and referred to a young 

 Iguanodon, in which the base of the centrum is fiat, with a sharp 

 ridge margining each side. 



There are two vertebrae which appear to be caudal — one from 

 the early part of the tail, the other from the later part of the tail. 

 Both appear to have been equally long ; and both are crushed. The 

 earlier caudal vertebra, as preserved, has the centrum about 4| centim. 

 long, and 22 millim. wide in the middle of the base. The anterior 

 face appears to have been concave, and, as preserved, is 4| centim. 

 deep ; the depth of the posterior end of the bone is somewhat less. 

 The base is flattened, though concave in length, and separated from 

 the sides by a sharp angular ridge. The sides of the bone are con- 

 cave. The transverse process appears to have been placed on the 

 hinder part of the centrum, below the neural arch, and to have had 

 an antero -posterior extent of no more than 17 millim. The neural 

 arch is compressed from side to side and constricted from back to 

 front, with a rounded ridge margining the straight outer border of 

 the neural arch, which is inclined obliquely backward. The zyga- 

 pophyses are imperfectly preserved. The posterior zygapophyses 

 extend beyond the centrum ; of the anterior zygapophyses no trace is 

 preserved. The later caudal vertebra has a constricted dicebox-like 

 form. Its contour appears to have been five-sided at the articular 

 ends, with a median ridge on the base and lateral ridges at the middle 

 of the sides. The length of the centrum is about 5 centim. Its 

 depth appears to be about 3 centim., and its width 3| centim. This 

 I take to be at the posterior end of the bone. Only an indication 

 of the neural arch is preserved ; the width of the canal increases pos- 

 teriorly as usual. Another vertebra, apparently dorsal, is imbedded 

 in the matrix ; but I have not felt justified in excavating it so as fully 

 to display its characteristics. 



Dermal Armour. 



The dermal armour comprises plates of two patterns : — first, more 

 or less circular plates of moderate thickness ; and angular plates 

 which are thick at one margin, thin at the opposite margin, and have 

 the surface concave in one direction and convex in the other. They 

 are flat on the under side. One or two of the small biscuit-like 

 plates present that curious angular combination of fibres that is cha- 

 racteristic of the armour referred to Hyloeosaurus, a character which 

 rather suggests the etched surface of a meteorite than the structure 

 of ivory. I have been led to think that this armour of Hylseosaurian 



