are removed from their place, and are scattered over the mass of shale in which they are imbedded. In consequence of this accident, we are admitted to a full view of the ribs and sterno-costal arcs and pelvis which remain undisturbed. Fourteen large ribs may be counted, and twenty-one dorsal or lumbar vertebrae appear dispersed, though their exact original number cannot be ascertained. The last of these lies over the pubis, and has, close to it, a short false rib.
Twenty-three caudal vertebra; are remaining; and as about 3 of the extreme ones appear to be wanting, we may probably assume this part at about 26 joints, the whole vertebral column then will number about 90 joints, viz. 35 cervical, 6 anterior-dorsal, 21 dorsal and lumbar, 2 sacral, and about 26 caudal. The proportions of the whole of these parts will stand nearly thus : taking the head as I, the neck will be as 5, the body as 4, and the tail as 3, the total length being, as was before remarked, 13 times that of the head.
The chevron bones beneath the tail are finely exhibited ; but this part, having been fully described in my former papers, suggests no new remarks, excepting that its shortness must have prevented its being used, as in fishes, as an instrument of impulsion in a forward direction, and that it was therefore probably employed only as a rudder to steer the animal by horizontal flexure, or by a sudden vertical stroke to elevate or depress it while swimming through the water.
The anterior sternal portion is greatly concealed by the vertebras and ribs lying over it: these might be carefully removed and replaced, and the structure of this important part ascertained. From several imperfect specimens which I have examined, it appears to have been complicated in its structure, and nearly to have resembled that of the tupinambis.
The posterior part of the sternum consists of a central bony arc, crescent-shaped, and swelling in the middle ; to its horns are applied two sterno-costal branches, which appear as usual to have been connected with the extremities of the ribs by cartilages : the nice adaptation of these parts is beautifully displayed in the specimen.
The pelvis is finely displayed, and resembles the usual type of this part in reptiles, of which the turtle perhaps affords the best example for comparison with the fossil : the ilium is reduced to a long and slender bone, which might, if seen detached, be mistaken for the os pubis ; that of several species of turtle is exactly similar. The ischium is like that of most reptiles ; and the pubis, as is also common in this class, is so greatly dilated as lobe liable to be mistaken for the ilium if found separately. All these parts are very nearly in situ, and the manner in which they unite to form the acetabular socket is easily perceived ; the oval formation between the ischium and pubis is also quite distinct.