THECOSPONDTLTJS DAVIESI. 81 



The anterior end of the vertebra (fig. 1 ) is imperfectly preserved, 

 having lost the cervical ribs and adjacent tissue of the neural arch 

 to which they were attached, as well as the adjacent prezyga- 

 pophyses. If these parts were restored they probably would ap- 

 proximate in shape to those of Coelurus fragilis, Marsh, except that 

 the lateral extension of the ribs was less, and their supra-neural 

 development was much less, for the lateral expansion of the neural 

 arch has a relatively higher position than in that genus. As pre- 

 served, the anterior aspect of the bone is remarkable for narrowness 

 relatively to its height. The articular face of the centrum (fig. 1,«) 

 is flat or slightly concave, inclined slightly forward, subquadrate, 

 being horizontal on the neural surface above, vertical laterally, and 

 on the base it is concave from side to side, owing to the anterior 

 corners having a downward development to form the basal attach- 

 ments for the cervical ribs (fig. 1, p). The transverse width of the 

 articular face of the centrum is 19 millim., and its vertical depth 

 in the middle is about as much. The margins are somewhat worn, 

 and show large cells defined by delicate tissue. The subtriangular 

 facets of the cervical ribs at the inferior anterior corners of the 

 centrum are probably but little worn, and in a line with the 

 original sutures. They are oblique, and look downward, forward, 

 and outward, and measure 13 millim. long by 9 millim. wide in 

 front, where they are separated by an interspace of half a centi- 

 metre, which is convex as it descends from the articular surface on 

 to the base of the centrum. The surface of the rib-facets is divided 

 into two or three cells. 



Above the articular face of the centrum is the transversely ex- 

 panded subhexagonal entrance to the neural canal, 2-^ centim. 

 wide and half as high in the middle, where the thin transverse bony 

 plate which forms the upper limit of the arch exteuds from side to 

 side with a downward curve. The neural canal itself (fig. 1, n. c) is 

 higher than wide. The lateral angular expansions or antrum in 

 front of the canal contain on each side an oval transversely oblique 

 foramen {pn)^ which was probably pneumatic. It is situate in the 

 lateral angle of the arch in such a way that the bone above it ap- 

 pears as though excavated, and that below it descends to form the 

 stout pedicle of the neural tunnel,which has a transverse measurement 

 of half a centimetre. The plate which limits the neural canal above 

 is 8 millim. behind the articular face of the centrum. Upon this 

 plate is a large aperture of a cavity in the neural arch, apparently 

 penetrating conically, which is only inferior in size to the nenral 

 canal. It is 12 miUim. wide at the base, and about 8 millim. high, 

 with the sides converging upward to a transverse width of half a 

 centimetre, while the upper border is 2 centim. behind the articular 

 face of the centrum. The cavity penetrates far into the bone, and 

 I regard it as having given attachments to ligaments which were 

 attached to the extremity of the neural spine. The whole supra- 

 neural region retreats backward as it ascends. Above this neural 

 cavity is a circular foramen about 4 millim. in diameter, which 

 assists in completing the triangular contour of the area above the 

 Q. J. G. S. No. 173. G 



