Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/133

1869.] physes of the antecedent vertebra laterally. The postzygapophyses of the first vertebra are completely ankylosed with those of the second; and those of the second seem to have been similarly united with those of the third. The centrum of the first vertebra, on the other hand, is not absolutely fused with that of the second, the separation being everywhere traceable; and the union between the centra of the second and third vertebræ seems to have been still more lax. Each neural arch is connected only with its own centrum, and the inter-vertebral foramen lies over the posterior moiety of each centrum.

A strong, prismatic sacral rib with a triangular section, only the proximal end of which remains, springs from the junction of the centrum with the neural arch on each side, in the first vertebra, and appears to have been directed perpendicularly outwards. The second vertebra seems to have possessed a similar rib, which, however, springs rather further back from the anterior edge of the arch. The third vertebra also possesses a strong rib, the root of which occupies the middle of the arch. The contour of the broken end of the rib is more nearly four-sided. The anterior and posterior faces are concave from above downwards, and are directed obliquely, the anterior upwards, and the posterior downwards. The centrum of the anterior vertebra is 1⋅6 inch long, that of the third 1⋅75 inch; but the difference may be the result of the crushing of the vertebræ, which are a good deal distorted. The height of the centrum seems to have been about 1⋅3 inch, the width about 1⋅1 inch.

Mr. Kirshaw has sent me two centra of vertebræ, which may very well have belonged to the same animal as the sacrum. One of these is almost undistorted, and belongs to the dorsal region. It is 1⋅6 inch long; and the better-preserved articular surface is 1⋅55 inch high, while its greatest width is rather less than 1 inch. The surface is very slightly concave, and is perpendicular to the axis of the centrum. The centrum is much constricted, so as to be not more than 0⋅6 inch wide in the middle; and, as in the other vertebræ, the floor of the neural canal sinks rapidly from each end towards the middle of the centrum. Some of the vertebræ from the Bristol conglomerate bear an extraordinarily close resemblance to these.

The fragmentary vertebra described and figured by Professor Owen as belonging to Labyrinthodon pachygnathus has the same general characters as those now described. The vertebra ascribed to Labyrinthodon leptognathus, on the other hand, appears to have belonged to some other reptile.

The remarkable ilium ascribed to Labyrinthodon pachygnathus (l. c. pl. 45. figs. 16, 17) is also a reptilian bone, intermediate in its characters between the ilium of a Teleosaurian and that of a Lizard. It is very similar to an ilium from the Keuper described and figured by Von Meyer ('Palæontographica,' Bd. vii. pl. 41), and ascribed by him to Belodon. I propose to discuss the nature and signification of this remarkable bone in another communication.

I have no direct evidence of the presence of Dinosauria in the Elgin sandstones; but ample proof is in my possession that the