WEALDEN DINOSAURS. 335 



Several specimens of dorsal vertebrae of the Megalosaurus, with the spinous pro- 

 cess broken away, have come under my observation. The largest of these, preserved 

 in the Geological Museum at Oxford, gives the following dimensions : 



In. Lines. 



Length of centrum . . . . . . .4 6 



Height of ditto . . . . . .4 3 



Breadth of ditto across articular surface . . . . .3 9 



Breadth of ditto across the middle part . . . . .2 6 



The proportions and configuration of the neural arch agree with those of the more 

 perfect vertebrae from the Wealden at Battle. The height of the spinous process of 

 this vertebra, according to that marked ns" in PI. 24, would not be less than 

 18 inches. 



The upper part of the centrum is impressed by the spinal canal, which expands at 

 each end, but chiefly behind. One or two vascular canals are sometimes present at 

 the under part of the centrum, but are neither so large nor so regular as in the 

 Plesiosauri. 



Compared with the Iguanodon (see PI. 3, of the Chapter on the ' Fossil Reptiles 

 of the Cretaceous Formations'), the sculptured sides of the neural arch are lower in 

 proportion to their length in the Megalosaur : the anterior zygapophyses are 

 more produced and more angular ; the posterior ones are less produced. The 

 depression anterior to the buttress, d, is bounded by the converging buttress or 

 ridge, b, but this seems not to have been developed in the Iguanodon, in which the 

 nearest approach to it is the elevated parapophysis in certain vertebrae, as in 

 that figured in PI. 3 {Dinosaurid), p- There does not appear to have been, in the 

 Iguanodon, the depression answering to that in front of the buttress, b, in PI. 24. 



It would seem, from the mutilated lumbar vertebrae of the Megalosaurus in the 

 Oxford Museum, figured in Dr. Buckland's original Memoir, pi. xlii, fig. 2, that the 

 anterior oblique buttress, b, subsided in the vertebrae in that region. 



Sacral vertebra. PI. 25. 



The sacrum of the Megalosaurus (PI. 25) consists of five anchylosed vertebrae, and it 

 is remarkable, considering how small a proportion of the recognisable bones of this 

 rare reptile has been found, that the present characteristic part of the vertebral 

 column of tliree diff'erent individuals should have been obtained : one sacrum, from 

 Stonesfield, is in the Geological Museum at Oxford ; a second sacrum, from Drv 



