Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/640

546 distally it becomes compressed and is apparently to some extent crushed from above downward, though an uncompressed fragment is 3 inches in thickness. The internal aspect is concave in length, and the external aspect convex. Both lateral margins appear to have been moderate^ concave; but the anterior margin is imperfect distally; if preserved it would probably have made the bone 9$1⁄2$ inches wide. The distal articular margin for the bones of the forearm is nearly straight; and the surface for the radius does not make an angle with the surface for the ulna. The bone was unusually massive, and relatively to the vertebræ is much longer and broader than in Dr. Hector's Mauisaurus Haastii.

The femur is imperfect at both ends. The fragment preserved is 13 inches long. The proximal end of the bone is nearly cylindrical and about 4 inches in diameter. The anterior margin of the bone is very slightly concave, so as to be nearly straight; the posterior outline is deeply concave.

The phalanges appear to have been compressed from above downwards and unusually long. Only one has been found (Pl. XXIII. fig. 6) imperfectly preserved; it is about 4$1⁄2$ inches long, 1$1⁄2$ inch wide where most constricted in the middle, and was probably 2 inches wide at the extremities.

In the lower dorsal region of the animal about a peck of ovate and rounded pebbles occurred, varying in size from a diameter of a quarter of an inch to a length of nearly two inches. They are chiefly of opaque milky quartz. Several are of black metamorphosed slate, and a few of altered fine-grained sandstone and hornstone, some of the pebbles showing a veined character, such as might be derived from the neighbouring Palæozoic rocks of the North of France. Pebbles being of such rare occurrence in the Gault, it would seem natural to account for these associated stones on the hypothesis that they were swallowed by the animal with food, as is the case with certain living reptiles and birds. If this view should be held admissible, it would suggest that as the teeth were too small for any thing but prehension, a structure analogous to a gizzard, or the stomach of an edentate, may have used these pebbles to assist in breaking up or crushing the food on which this Saurian lived.

Fig. 1. Prehensile tooth, of the plesiosaurian type, a, crown; b, fang. Nat. size.

2. Middle cervical vertebra, side view.

3. Late cervical vertebra, with the pedicle (t) for the ribs rising above the sides of the centrum.

4. Pectoral vertebra with the pedicle for the rib formed partly by the centrum and partly by the neural arch.

5. Dorsal vertebra, showing the broken transverse processes (t), and base of the neural spine. In the British Museum.

6. Phalange, imperfect; natural size.