of the base of the centrum external to the ribs is 278 inches. The bases of the ribs are strong, elevated, and directed chiefly downward. The sides of the centrum are smooth, concave from front to back, and moderately convex from above downward, and extend vertically for 1 inch above the ribs; the neural arch is confluent with the centrum, and unites with it by a large compressed squamose base, which fits into an impressed concave area.
The fourth specimen is 334 inches long; and the whole centrum is somewhat larger, with flatter articular faces and deeper excavations on the base of the centrum. The fifth, a trifle longer, shows the neural canal as a deep channel, concave from front to back, and at least an inch wide. The articulation for the rib is nearer towards the anterior margin of the centrum, where the process is thicker than posteriorly; as fractured it is 178 inch long. The seventh centrum is 4 inches deep and about 14 inch wider; so that the articular face has become morecircular. This surface is much flatter, but now has a shallow central concavity an inch in diameter. The centrum is 412 inches long; its basal excavations are more elongated, and the upper part of the centrum is more compressed. The eighth centrum is larger in the articular faces. The neurapophyses are remarkably extended from front to back, and greatly compressed, each being less than 14 inch thick. On the base, separated by the rounded median ridge, are two large oval nutritive foramina about 34 inch apart. The bases of the ribs grow stronger and are 78 inch in depth. The tenth centrum is 414 inches long, with the articular face as deep and 518 inches wide, though the width over the articulations for the ribs is somewhat less. In the eleventh the base for the rib has become more ovate and larger, and the base of the neural canal has increased with the size of the vertebra, the neural arch being 2 inches wide externally behind.
The thirteenth vertebra has the neural arch well preserved (Pl. XXIII. fig. 2). The centrum is 4 inches in antero-posterior length. Its anterior face is 534 inches wide and about 412 inches deep. It has a central depression 2 inches broad, margined by an elevated rounded rim, between which and the circumference is a second concave area in the form of a ring, but less deep. The posterior articulation is 6 inches broad and 412 inches deep; it has the transversely oval central area shallow, but without the elevated rim. The base of the centrum is 414 inches long; it is convex from side to side, with an obtuse median ridge. The distance between the articulations for the ribs is 514 inches. The articular surface for the rib is subcircular, l34 inch deep, and near]y 112 inch from front to back; this area is 34 inch from the posterior margin and more than 112 inch from the anterior margin of the centrum. The lateral area above the articulation for the rib is flattened, concave from side to side, and scarcely concave in depth. And the neural arch rises steadily from the side of the centrum without any break to a height of 1012 inches, being imperfect superiorly. The neural arch is much compressed from side to side. The posterior zygapophyses hang entirely behind the posterior articular face of the centrum ; they are close together, being
