CAUDAL VERTEBRAE OF HESPERORNIS. 83 



Measurements of Sixth Caudal Vertebra. (No. 1200.) 



Length of centrum, 13.5 mm 



Transverse diameter of anterior articulation, 11.0 



Transverse diameter'of posterior articulation, 10.0 



Length of floor of neural canal, 13.5 



Length of roof of neural canal, 10.0 



Transverse diameter of neural canal, at anterior opening, 2.5 



Vertical diameter of neural canal, at anterior opening, 2.5 



Transverse diameter of neural canal, at posterior opening, 2.0 



Vertical diameter of neural canal, at posterior opening, 3.8 



Antero-posterior diameter of transverse process, at base, 8.0 



The Seventh Caudal Vertebka. (Plate XII, figure 7.) 

 In the seventh caudal vertebra, the centrum becomes still more slen- 

 der, and the transverse processes reach then greatest lateral expansion. 

 The articular faces of the centrum are concave, and broadly oval in out- 

 line. The transverse processes pass off from the posterior half of the 

 centrum, and extend directly outward, and somewhat backward. They 

 are broadly expanded horizontally, and then- extremities are abruptly 

 truncated. The hypapophysis, which articulates with the posterior lower 

 margin of this vertebra, has become coossified with the centrum of the suc- 

 ceeding vertebra. The neural arch is placed well forward. The neural 

 canal is much reduced, and the neural spine was weak, and short. 



Measurements of Seventh Caudal Vertebra. (No. 1200.) 



Length of centrum, 13.0 mm 



Transverse diameter of anterior articulation, 10.2 



Vertical diameter of anterior articulation, 8.0 



Transverse diameter of posterior articulation, 8.0 



Vertical diameter of posterior articulation, 7.0 



Length of floor of neural canal, 14.0 



Transverse diameter of neural canal, at anterior opening, . 3.0 



Vertical diameter of neural canal, at anterior opening, 3.0 



Diameter of vertebra, across transverse processes, 59.0 



Antero-posterior diameter of transverse process, at base, 8.0 



The Eighth Caudal Vertebka. (Plate XII, figure 8.) 

 The eighth caudal vertebra of Hesperornis regalis has the centrum 

 constricted medially, and shorter than that of the seventh. Its coossified 

 hypapophysis was pointed in front, and projected beneath the posterior 



