CERVICAL VERTEBRAE OF HESPERORNIS. 



35 



Transverse diameter cf vertebra, across post-zygapophyses, .-- 32.8 mra 



Greatest diameter of pre-zygapophyses, 13.0 



Least diameter of pre-zygapophyses, 10.2 



Greatest diameter of post-zygapophyses, _ 12.2 



Least diameter of post-zygapophyses, 10.0 



Length of floor of neural canal, 22.0 



Length of roof of neural canal, 16.0 



Transverse diameter of neural canal, at anterior opening, 9.0 



Vertical diameter of neural canal, at anterior opening, 6.6 



Transverse diameter of neural canal, at posterior opening, 9.0 



Vertical diameter of neural canal, at posterior opening, - . 6.0 



Total length of pleurapophysis, 25.0 



Length of free portion of pleurapophysis, 15.0 



Diameter of pleurapophysis, at base, . 7.0 



Transverse diameter of lateral foramen, - . 10.0 



Vertical diameter of lateral foramen, 7.5 



The Thirteenth Vertebra. (Plate IV, figure 4.) 



The thirteenth vertebra in many respects resembles the twelfth, and 

 is of about the same length. It is rather more excavated at the sides, and 

 has apparently a somewhat larger lateral foramen. The neural spine is 

 but slightly indicated, and in this and the next vertebra reaches its mini- 

 mum of development. The anterior and posterior zygapophyses approach 

 still nearer to each other, to aid the flexure of the neck, which is greatest 

 at this point. The descending processes are short and stout, and the 

 pleurapophyses much as in the twelfth vertebra. 



The figures given below represent the anterior and posterior aspects 

 of the vertebra here described. 



Figube 8. — Thirteenth vertebra of Hesperornis regalis, Marsh; (No. 1207), front view; natural size. 

 Figure 9. — The same vertebra; posterior view. d. diapophysis ; p. parapophysis ; /.lateral foramen; 

 nc. neural canal ; s. neural spine ; z. pre-zygapophysis ; z'. post-zygapophysis. 



