Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/465

 rity to mine. Unfortunately the comparison cannot be extended to their form, since my arch &c. wants nearly the entire centrum, and the British Museum centrum bears only a very worn and mutilated upper structure. Their identity must therefore be left at present undetermined *.

Two of the leading features in the frame of this new vertebra, the median wedge and notch (accessory to the ordinary articulating surfaces of the zygapophyses), and the broad platform, point in the direction of Dinosauria. The wedge and notch (similar in principle, but differently placed to the zygosphene and zygantrum of Snakes), which, till very lately, I believed to be peculiar to this vertebra, are present also, Prof. Huxley tells me, in Megalosaurus ; and the platform upon the neural arch is one of the marks of Iguanodon Mantelli.

Dimensions.

inches.

Neurapophyses, length (from front to back) about 5

,, height to top of neural canal, about 5

,, „ crown of arch 6

Praezygapophyses. Upper articulating surface.

Transverse diameter (or from median to outer border) 3.2

Antero-posterior diameter 1.9

Interpraezygapophysial notch.

(Antero-posterior) length 2

Width, behind .7

„ in front 1.3

Vertical wedge beneath the postzygapophyses.

Vertical depth 2

Thickness .9

Transverse process.

Length along upper surface 3.5

Costal articulating surface, vertical diameter 2.5

Horizontal diameter 1.1

Platform (broader than) 5

Neural spine (pillars), length 7

is this Streptospondylus ? The vertebra is in the North Gallery. It bears the Catalogue number 28632, and also a written label with the words " Wealden, S.E. England ; " and it formed part of the Mantellian collection. It differs from all the other opisthocoelian vertebra in the National Collection, not merely in its texture, but also in its form and proportions, and more particularly in the presence of a very large and deep excavation in the side of the centrum, nearly perforating it, beneath the neural canal. In position, this pit corresponds, as Mr. Seeley has lately pointed out, to the pneumatic foramen of the Pterodactylian vertebra. But should any one be tempted to conjecture, from the presence of this pit, together with the very open texture of the bone, that this Streptospondylus was an enormous flying Saurian, he will do well to bear in mind that an extremely light skeleton does not necessarily prove endowment with flight, and also that all Pterosaurian vertebrae yet known are procoelian, and what perhaps is of minor importance, that the horizontal diameter of their articular
 * Should it hereafter be established, there will still be the question, What