24 ODONTORNITHES. 



Transverse diameter of vertebra, across post-zygapophyses, 29. m 



Greatest diameter of pre-zygapophyses, - 9.0 



Least diameter of pre-zygapophyses, 4.5 



Greatest diameter of post-zygapophyses, 9.6 



Least diameter of post-zygapophyses, 8.2 



Length of floor of neural canal,. 24.5 



Length of roof of neural canal, .. 24.0 



Transverse diameter of neural canal, at anterior opening, 8.5 



Vertical diameter of neural canal, at anterior opening, 5.2 



Transverse diameter of neural canal, at posterior opening, 9.0 



Vertical diameter of neural canal, at posterior opening, 6.0 



Measurements. (No. 1474.) 



Length of centrum, 24.0 n 



Vertical diameter of anterior articulation of centrum, 5.0 



Transverse diameter of posterior articulation of centrum, 11.0 



Vertical diameters of posterior articulation of centrum, 1.5-1 1.0 



Length of floor of neural canal, 26.0 



The Fifth Vertebra. (Plate III, figure 4.) 



The fifth vertebra is a little longer and larger than the fourth, to 

 which in most respects it is similar. The centrum, however, is not so 

 much excavated in the postero-lateral region. The ridge above the groove 

 entering the lateral foramen is more pronounced. The ventral side of the 

 centrum is less deeply hollowed out behind the anterior articulation, and 

 the depression blends more gradually with the general under surface, which 

 bears no hypapophysis, but is excavated throughout its length. The 

 articular surfaces are much as in the fourth vertebra, with the inferior por- 

 tion of each a little more expanded. The pre-zygapophyses slope 

 somewhat inward, and the post-zygapophyses are surmounted by a 

 tubercle pointing outward and backward. The lateral foramen is larger 

 than in the fourth vertebra, and the pleurapophysis longer. The base of 

 the neural spine stops a little short of the anterior margin of the roof of 

 the neural canal, and terminates at a notch posteriorly. 



The measurements given below of the fifth cervical vertebra of 

 Hesperomis regalis are derived from two different specimens, numbers 

 1206 and 1207. 



