CERVICAL VERTEBRA OF HESPERORNIS. 25 



Measurements of Fifth Vertebra. (No. 1206.) 



Length of centrum, 28.0 mm 



Transverse diameters of anterior articulation of centrum, 11.0-13.0 



Vertical diameters of anterior articulation of centrum, 6.0- 9.0 



Transverse diameters of posterior articulation of centrum, 10.0-15.0 



Transverse diameter of vertebra, across pre-zygapophyses, 27.0 



Transverse diameter of vertebra, across post-zygapophyses, 27.5 



Diameters of post-zygapophyses,. 8.0-10.0 



Transverse diameter of lateral foramen, 3.5 



Vertical diameter of lateral foramen, 6.5 



Length of pleurapophysis, 25.0 



Length of free portion of pleurapophysis, 17.0 



Measurements. (No. 1207.) 



Length of centrum, 28.0 mm 



Least transverse diameter of centrum, 1.8 



Transverse diameters of anterior articulation of centrum,-^ 11.0-13.0 



Vertical diameters of anterior articulation of centrum, 5.5- 8.0 



Vertical diameter of posterior articulation of centrum, 8.0 



Transverse diameter of vertebra, across pre-zygapophyses, 27.0 



Transverse diameter of vertebra, across post-zygapophyses, 28.0 



Greatest diameter of pre-zygapophyses, 10.0 



Least diameter of pre-zygapophyses, 5.5 



Greatest diameter of post-zygapophyses, 10.0 



Least diameter of post-zygapophyses, 8.0 



Length of floor of neural canal, 28.0 



Length of roof of neural canal, 27.5 



Transverse diameter of anterior opening of neural canal, 9.0 



Vertical diameter of anterior opening of neural canal, 6.5 



Transverse diameter of lateral foramen, 3.5 



Vertical diameter of lateral foramen, — 5.0 



The Sixth Vertebra. (Plate III, figure 5.) 



The sixth vertebra is larger than any of the preceding, and in general 

 form resembles the fifth. The ridge on the side of the centrum, above the 

 excavation for the lateral foramen, is continued downward and backward, 

 until it falls into the much more prominent ridge, or crest, separating the 

 lateral and ventral surfaces of the centrum. This latter ridge is strongly 

 developed. Arising near the lower external angle of the front articulation, 

 it first forms a considerable floor for the groove of the vertebral artery ; 

 and then is continued backward, and terminates on each side in a tubercle, 

 4 



