CERVICAL VERTEBRAE OF HESPERORXIS. 29 



Transverse diameter of vertebra, across post-zygapophyses, 21.0 mm 



Greatest diameter of pre-zygapophysis,. 10.5 



Least diameter of pre-zygapophysis, _ 6.4 



Greatest diameter of post-zygapophysis, 12.0 



Least diameter of post-zygapophysis, 8.0 



Transverse diameter of neural canal, at anterior opening,. 9.0 



Vertical diameter of neural canal, at anterior opening, 6.5 



Length of pleurapophysis,. 81.0 



Diameter of pleurapophysis, at base, 6.5 



Vertical diameter of lateral foramen, - . — 6.5 



Transverse diameter of lateral foramen, 3.4 



The Eighth Vertebra. (Plate III, figure 7.) 



The eighth vertebra is the largest cervical of the series, slightly 

 exceeding both the seventh and the ninth in length. It closely resembles 

 the seventh, being slightly larger in nearly all its dimensions. The ventral 

 surface of the centrum is more broadly and deeply excavated anteriorly 

 than in the seventh, and the tubercles, or processes, on each side of this 

 excavation are more developed, and considerably incurved. They stand 

 somewhat wider apart at their bases than in the seventh vertebra, and the 

 whole under surface is more widely excavated. The two tubercles near 

 the posterior end of the lower surface are small. The lateral ridge, start- 

 ing at the upper end of the foramen for the vertebral artery, fades out 

 upon the side of the centrum earlier than in the preceding vertebra. The 

 diapophysis is somewhat stronger and larger than in the seventh vertebra, 

 and the foramen itself is larger. 



The neural spine is shorter than in the seventh cervical. It tapers 

 rapidly almost to a point above, and terminates posteriorly at the margin of 

 the neural arch. The latter shows no median notch at this point, as in the 

 preceding vertebrae, the margin being gently and evenly excavated between 

 the zygapophyses. The pre-zygapophyses are slightly convex, and the 

 post-zygapophyses concave. The latter are strengthened by a ridge 

 running along the side of the neural arch, and rising and becoming more 

 prominent over the zygapophyses. The articular surfaces of the centrum 

 are larger, and especially broader, below, than in the seventh vertebra. 

 The pleurapophyses are of nearly the same length as in that vertebra. 



