Edestosaurus rex Marsh, op. cit. iii, p. 462, pl. xxii, f. 1, June, 1872.
C. planifrons.
Clidastes planifrons Cope, Bullet. U. S. Geol. Surv. No. 2, p. 31, 1874; Cret. Vert. etc. pp. 135, 265, pls. xxii, xxiii.
C. Westii.
C. Westii Williston, n. sp. infra.
CLIDASTES VELOX.
A remarkably complete specimen, referred with considerable certainty to this species, was obtained by ourselves in western Kansas, (Butte Creek) in the summer of 1891. A brief preliminary description of the specimen was given by the senior author in Science, December 8, 1891. A more complete description is here given, which, it is believed, will be of service. The specimen is an unusually perfect one, being very nearly complete, and, as now mounted, shows the bones nearly all in the position in which they were found. The vertebral column is continuous, except in one place, where the tail had been bent up over the back; and complete, save at the very tip of the tail. The skull is complete, or very nearly complete, and has been restored nearly to the condition in life. Figures have been made of this portion of the skeleton, and will be given in a future communication. At present, it may be mentioned that the lacrymals are small, roughly irregular bones, and pointed at either extremity. There are no indications of transverse bones, as there are none in any other skull in the collection.
Cervical vertebrae.
Atlas. The intercentrum is a small bone with three sides of nearly equal extent. The two upper, articular surfaces are gently concave, and meet in a rounded margin; the inferior surface is convex, both antero-posteriorly and transversely, with a roughened prominence in the middle. The lateral pieces have indistinctly separated facets for articulation with the odontoid, the intercentrum and the occipital condyle. The rather short, flattened lamina extends upward, backward and inward, approaching, but not reaching its fellow of the opposite side; it is somewhat dilated distally. Directed outwards and forwards, there is a stout styliform process.
Axis. The neural spine of the axis is elongated antero-posteriorly. It is thin on the anterior portion, but stouter and longer at the posterior part. The large, stout odontoid process is united suturally, as is also the well-developed atlantar hypapophysis, which forms the anterior, inferior portion of the bone. The diapophyses are the smallest of the costiferous series, with only a small articular facet for the rib. The ball is strongly and evenly convex, with its greater diameter transversely. The hypapophysis is the largest of the series; it is suturally united with the stout, exogenous process of the centrum, and projects downward and backward; its distal extremity is roughened for ligamentous attachments.