CAUDAL VERTEBRAE OF HESPERORXIS. 81 



Measurements of Fourth Caudal Vertebra. (ISTo. 1200.) 



Length of centrum, 12.0 rum 



Least diameter, below transverse processes, 1.5 



Transverse diameter of anterior articulation, 11.5 



Vertical diameters of anterior articulation, 9.2-11.0 



Transverse diameter of posterior articulation, 1 0. 2 



Vertical diameters of posterior articulation, 9.5-10.0 



Diameter of vertebra, across transverse processes, 32.0 



Length of floor of neural canal, 10.5 



Length of roof of neural canal, 8.2 



Transverse diameter of anterior opening of neural canal, 4.0 



Vertical diameter of anterior opening of neural canal, 5.0 



Transverse diameter of posterior opening of neural canal, 4.0 



Vertical diameter of posterior opening of neural canal, 4.5 



Height of neural spine above floor of neural canal, 19.0 



Least antero-posterior diameter of transverse processes, 6.5 



Transverse diameter of shaft of neural spine, 3.0 



Transverse diameter of head of neural spine, 7.0 



The Fifth Caudal Vertebra. (Plate XII, figure 5.) 



The fifth caudal vertebra of Hesperornis regalis is somewhat longer 

 than the fourth, but its centrum is narrower, and its articular faces 

 perceptibly smaller. The general form of the anterior articulation is 

 sub-quadrate in outline, with the corners rounded. It is notched above for 

 the neural canal, and has its lower border also indented on the median line. 

 Both articular facets are somewhat concave. 



The transverse processes are much longer than in the last vertebra, 

 and their distal ends are expanded horizontally. The axes of the descend- 

 ing portion of these processes bear the same relation to the axis of the 

 neural spine, as in the third vertebra, the three meeting in the neural canal, 

 and including equal angles with each other. The lower surface of the 

 transverse process extends somewhat below the ventral face of the centrum, 

 and then turns abruptly upward and outward, nearly to the extremity, 

 which is slightly deflected. Seen from above, ihe ends of these transverse 

 processes appear rounded, and their posterior margins project behind the 

 articulation of the centrum. The ventral surface of the body of this 

 vertebra is concave in a fore and aft direction, and convex transversely. 



