expense of much labour and judgment. One is the remains of a well-developed individual ; but little more than vertebrae and a few of the ribs in a more or less dilapidated state are preserved ; but on another slab three or four perfect ribs have occurred. The other specimen is in a much more perfect condition, the principal bones of three of the limbs being well displayed as well as one of the fore feet and most of the ribs, which lie in regular order on either side of the vertebral column. The former, as already mentioned, is undoubtedly the remains of Proterosaurus Speneri, and the latter a new species of the same genus, Proterosaurus Huxleyi.
Proterosaurus Speneri, v. Meyer. (Pl. XXXIX.)
The bones of the specimen of this species are in a very perfect condition, the surface of them being quite intact, and in places having even a semigloss. The vertebrae are lying articulated in a much curved line, the animal having apparently died with the spine arched violently backwards, as seems to have been the case with all the examples hitherto obtained. In our specimen the curve is even more sharp than usual, the remains of the column forming almost half a circle. The anterior portion of it is thrown suddenly back, and at the pelvic region it is as suddenly bent upwards.
In all there are thirty-five or thirty-six vertebrae and casts of vertebrae in continuous order, measuring, if placed in a right line, 22 inches in length. Of these vertebrae twenty-one appear to belong to the trunk, and fifteen or sixteen are caudal. Now if we deduct two or three for the lumbar vertebrae, there will remain seventeen or eighteen dorsal vertebrae. Meyer concluded, after carefully enumerating the joints in all the known individuals, that the number is "not under sixteen, and not over nineteen;" so that it would appear that the whole of the dorsal vertebrae are present, in front only the cervical being deficient. As Meyer estimates the tail-joints at more than thirty-six or thirty-eight, it would then appear that more than half of them are wanting in the specimen before us.
The centrum of the dorsal vertebrae is upwards of | inch long, and about 1/2 inch in height. In one of the largest specimens figured by von Meyer (tab. ix.) it is 7/8 inch long and 1/2 inch high. It would therefore seem that the Midderidge example is full-grown and a large individual. It is impossible to observe the ends of the vertebrae, as they are all articulated; but from the appearance of the joints where they gape a little, it would seem that both the anterior and posterior articular surfaces are slightly concave, and their margins appear as if reflected ; the sides of the centrum are smooth and are a little concave.
The spinous process is inch high, being more than twice the height of the centrum, and it is an inch from back to front ; consequently it is considerably shorter than the body. It is much compressed, and is expanded a little above in the direction of the long axis of the vertebrae ; and the dorsal margin or crest is slightly arched in the same direction, and exhibits on the sides delicate
