30 ODONTORXITIIES. 



The principal dimensions of the eighth vertebra, as determined from 

 two specimens of Sesperomis rcgalis, are as follows : 



Measurements of Eighth Vertebra, (No. 1206.) 



Length of centrum, 33.0 mm 



Transverse diameters of posterior articulation of centrum, . 11.0-15.0 



Vertical diameters of posterior articulation of centrum, . 8.0-12.5 



Transverse diameter of vertebra, across post-zygapophyses (approximate),.. 22.5 



Diameters of pre-zygapophyses, .... 7.0—11.0 



Diameters of post-zygapophyses, 7.5-13.0 



Length of roof of neural canal, 30.0 



Total length of pleurapophysis, 33.0 



Length of free portion of pleurapophysis, 25.0 



Measurements. (No. 1207.) 



Length of centrum,.. 33.0™ m 



Least diameter of centrum, at base, — 9.S 



Transverse, diameters of anterior articulation of centrum, 12.0-17.0 



Vertical diameters of anterior articulation of centrum, 7.0-1 1 .0 



Transverse diameter of posterior articulation of centrum, .. 16.0 



Vertical diameter of posterior articulation of centrum, 9.0 



Transverse diameter of vertebra, across pre-zygapophyses, 30.0 



Transverse diameter of vertebra, across post-zygapophyses, 29.0 



Greatest diameter of pre-zygapophysis, 10.5 



Least diameter of pre-zygapophysis,. . , . 7.8 



Greatest diameter of post-zygapophysis, 12.0 



Length of roof of neural canal, 28.2 



Transverse diameter of neural canal, at anterior opening, 9.0 



Vertical diameter of neural canal, at anterior opening, 6.5 



Total length of pleurapophysis, 32.0 



Length of free portion of pleurapophysis, 21.0 



Diameter of pleurapophysis, at base, . .. 9.0 



Vertical diameter of lateral foramen, 8.0 



Transverse diameter of lateral foramen, 4.5 



The Ninth Vertebra. (Plate III, figm-e 8.) 

 The ninth vertebra has a centrum slightly shorter than the eighth, but 

 somewhat broader and stouter. The under surface of the centrum is 

 slightly broader, and is more deeply and widely excavated anteriorly. 

 This excavation, as in the preceding vertebra, is somewhat over-arched by 

 two descending incurved processes, which are longer and larger than in 

 the eighth vertebra, and are also set somewhat farther forward, so as to be 



