Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/636

542 no indication of this enormous number of vertebræ or length of neck; but the vertebræ are quite as large, and are larger than in any British long-necked Plesiosaurian hitherto described.

The tooth is perfect, and measures 1$3⁄4$ inch in length. The crown is $3⁄4$ inch long; it is curved inward and backward, and is flattened somewhat on its external aspect. The crown terminates in a point, and is marked with fine close-set parallel striations rather finer than is common among Plesiosaurs. The fang continues to expand for half its length, and then contracts somewhat towards the base, so that the convex anterior outline of the tooth is an arc of a smaller circle than the concave posterior border. It is difficult to estimate the size of the head from a tooth; but it probably did not exceed a foot in length.

The earliest vertebra preserved is an early cervical with the neural arch and cervical ribs ankylosed to the centrum. These short ribs give a subtriangular appearance to the articular surface, which is modified a little by the lateral widening of the neural arch. The antero-posterior length of the centrum is 1$1⁄16$ inch; the depth of the centrum is 1$1⁄8$ inch; and its breadth on the anterior face is 1$3⁄8$ inch. The articular face is flattened, moderately concave, and most compressed from front to back at the base of the neural arch. The base of the centrum is marked with an elevated median ridge. The short ribs are given off from the inferior lateral corners of the centrum, and, as usual, are directed outward, backward, and downward. The neural canal is large and vertically ovate; the neural arch is constricted from side to side at the base of the neural canal; it has a subquadrate aspect as preserved, but is too imperfect for description. I am aware of no data on which to determine the number of vertebræ which were anterior to this one, or which intervened between it and the next preserved.

The second of the series has the centrum nearly 3 inches long, with the articular ends flattened and slightly concave, and the margins of those surfaces slightly rounded. The centrum has an elongated constricted appearance, and has the compressed, elongated, elevated, articular area for the cervical rib at the base of the lateral aspect; but the specimen is too badly preserved to admit of measurement.

Many vertebræ are missing between the second and the next preserved; for although the third is only 3$1⁄2$ inches long, it has nearly twice the transverse diameter of the second. The articular faces, still a little concave, are transversely ovate, about 3$3⁄4$ inches wide, with the centrum 2$3⁄4$ inches deep in front and deeper behind. The edges of the articular margin are slightly bevelled. The base of the centrum has a strong median ridge, which becomes broader towards each articular surface. On each side of the base, between this ridge and the rib, is a large impressed crescentic area. The transverse width