WEALDEN DINOSAURS. 339 



specimen from Dry Sandford. The remaining vertebrae in this specimen are 

 characterised by the same smooth and polished surface, rich brown colour, contraction 

 of the middle of the body, its cylindrical form transversely, and the longitudinal fossa 

 below the annular part, as in the Oxford specimen. The length of this series is one 

 foot six inches and a half ; the second and third sacral vertebrae are rather shorte 

 than the rest. The first sacral vertebra, which was not anchylosed to the last lumbar, 

 gives the following dimensions : 



Antero-posterior diameter of centrum .... 



Vertical diameter of anterior ailieular end .... 

 Transverse diameter of anterior articular end 



The neural arch seems not to have been coextensive in length with the centrum, but 

 rests on its anterior three fourths. A strong and short parapophysis extends obliquely 

 upwards and backwards from each side of the arch ; the antero-posterior diameter of 

 the base of this process is two inches, its vertical diameter one inch and a half. In 

 the second sacral vertebra the neural arch has moved forward upon the interspace 

 between the first and second sacral bodies, and developes from the lower part of its 

 base a stronger, thicker, and longer parapophysis, directed outwards and forwards. 

 The third neural arch has its base transferred directly over the interspace of the second 

 and third centrums ; the diameters of the base of its parapophyses are three inches and 

 two and a half inches : they incline slightly backwards. The fourth neural arch 

 descends lower down upon the interspace between the third and fourth centrums. The 

 fifth neural arch, as in the Oxford specimen, extends a little way across the interspace 

 between the fourth and fifth centrums, but nearly resumes its ordinary place. The 

 second and third sacral vertebrae are not so regularly convex below in the transverse 

 direction, but their sides converge so as to give a slight indication of a broad obtuse 

 ridge. The diameter of the spinal canal in the first and last sacral vertebrae is one 

 inch. 



The specimen of a portion of the sacrum of the Megalosaurus in the British 

 Museum includes one of the sacral vertebrae and a great proportion of the next 

 vertebra. The characteristic shape of the inferior surface of the bodies of these 

 vertebrae is well shown in this specimen, in one of the vertebrae of which the 

 transversely rounded or convex surface begins to be modified into an almost carinate 

 form of that surface. A similar difference of the inferior surface may be noticed in 

 the third and fourth sacral vertebrae of the Iguanodon.* 



The five sacral vertebrae are not anchylosed in a straight line, but describe a gentle 

 curve, with the concavity downwards ; the series of parapophyses, or sacral ribs, forms 



* PI. 8. 



