CERVICAL VERTEBRiE OF HESPERORXIS. 23 



the centrum are much, as in the third vertebra, being slightly larger, and 

 presenting about the same obliquity. 



The neural arch is strongs flattened above, and strengthened behind 

 by a ridge, as in the third vertebra. The neural spine extended more than 

 half the length of the neural arch, and terminated behind just in advance 

 of a median notch. The anterior zygapophyses are elongated, and are 

 directed forward, upward, and a little more inward than in the third 

 vertebra. The post-zygapophyses are strengthened by a lateral ridge, as 

 in the preceding vertebra. The upper surface of the neural arch on each 

 side of the spine is less depressed posteriorly. The lateral foramen was 

 larger than in the third vertebra, and the pleurapophyses were longer, and 

 directed nearly horizontally backward. In one specimen (number 1206), 

 the median hypapophysial riclge is produced near the middle of the 

 centrum into a conspicuous pointed hypapophysis. 



The following measurements are taken from the fourth cervical 

 vertebra of two individuals of Hesperornis regalis, arid one^ number 1474, 

 of Hesjperomis crassipes : 



Measurements of Fourth Vertebra. (No. -120.6.) 



Length of centrum, 26.0 m,n 



Transverse diameter of anterior articulation of centrum, » 12.0 



Vertical diameter of anterior articulation of centrum, 5.0 



Transverse diameters of posterior articulation of centrum, 9.0-12.0 



Vertical diameters of posterior articulation of centrum, 7.0- 9.0 



Transverse diameter of vertebra, across pre-zygapophyses, -.-- 19.0 



Transverse diameter of vertebra, across post-zygapophyses, 26.0 



Diameters of pre-zygapophyses, _-' 7.0-12.0 



Diameters of post-zygapophyses, - - 9.0-1 1.0 



Length of floor of neural canal, - _- 26.0 



Length of pleurapophysis, _ 21.0 



Length of free portion of pleurapophysis, 1*7.0 



Measurements. (No. 1207.) 

 Length of centrum, 24.0 mm 



Least transverse diameter of centrum, .. 0.5 



Transverse diameter of anterior articulation of centrum,..,. 11.8 



Vertical diameter of anterior articulation of centrum,. 4.5 



Transverse diameters of posterior articulation of centrum, . 9.0-1 1.0 



Vertical diameters of posterior articulation of centrum, 8.0-10.0 



Transverse diameter of vertebra, across pre-zygapophyses, 21.0 



