120 Prof. H. G. Seeley on some Vertebrae and 



lateral thickening of the anterior terminal ridges at the sides, 

 apparently to form facets for the attachment of ribs, though 

 these facets are not well defined. Secondly, the prolongation 

 forward of prezygapophyses, which extend f inch in advance 

 of the face of the centrum, diverging as they extend outward 

 to a width of If inch. The upper articular surfaces of these 

 processes are flat, as though to allow of some lateral move- 

 ment, and the lower surfaces are convex. The extremities of 

 the facets curve downward, as though there were also some 

 degree of upward and downward movement of the slender 

 neck. There is the same median ridge on the base of the 

 centrum and similarly inclined parts form its base. It is 

 possible that the cervical vertebrse were of unequal length. 



Dorsal Vertebra. 



Only one dorsal vertebra is preserved. It is relatively 

 shorter than in Zanclodon, for while the atlas is four fifths as 

 long as that of Z. Quejistedti, this dorsal vertebra is less 

 than half as long. The centrum measures 1^ inch from front 

 to back, is compressed from side to side, with the sides flattened 

 and rounded at the base. The compression may be slightly 

 increased by distortion and fossilization. The anterior and 

 posterior faces are much deeper than wide, measuring Ijinch 

 deep by | inch wide, the width being a little greater in front. 

 The neural arch is compressed and defined from the centrum 

 by a longitudinal suture at the base of the neural canal, as in 

 Massospondi/lus carmatus. At the anterior border of the base 

 of the neural arch is the vertically ovate facet for the head of 

 the rib, which is flat and just raised a wafer thickness above 

 the level of the bone. It is fully ^ inch deep. The trans- 

 verse processes are directed outward and upward, more so 

 than in the anterior vertebrae of Iguanodon; so that in place 

 of the usual horizontal platform a concave channel appears to 

 lie on each side between them and the narrow neural spine, 

 which is \l inch from front to back and ^ inch thick. The 

 usual buttresses appear on the sides of the neural arch, the 

 anterior being a slight ridge ascending from the middle of the 

 summit of the rib articulation ; and the posterior, which is 

 longer and more concave, ascends from the hinder margin of 

 the centrum. These ridges are still separated by more than 

 ^ inch on the underside of the short transverse process, which 

 extends out | inch beyond the neural spine and rises 2^ inches 

 above the base of the centrum. The neural spine extends as 

 far back as the flattened posterior face of the centrum and as 

 far forward as the margin of the facet for the head of the rib. 



