DORSAL VERTEBRAE OF HESPERORXIS. 53 



Transverse diameter of vertebra, across parapophyses, 27.5 mm 



Length of floor of neural canal, 25.5 



Transverse diameter of neural canal, at posterior opening, 8.5 



Vertical diameter of neural canal, at posterior opening, 6.6 



Diameters of articulation for head of rib, 7.0- 8.0 



Height of neural spine above floor of neural canal, 38.0 



Antero-posterior diameters of neural spine, 14.0-20.0 



The Twenty-second Vertebra. (Plate V, figure 6.) 

 The twenty-second vertebra is slightly shorter than the twenty-first. 

 The centrum is stouter, and the articular faces are larger. The hypa- 

 pophysis is short, and rudimentary. Parapophyses can hardly be said to 

 exist, as the articular surface for the head of the rib is only elevated at its 

 margin above the general surface of the vertebra. The diapophyses are 

 short, and at the end tubercular, as in the next vertebra. They are directed 

 somewhat downward and forward, with indications of a groove and pit in 

 front, as on most of the preceding dorsals. The neural spine is higher 

 than in the preceding vertebrae. 



The following tables contain the dimensions of four examples of the 

 twenty-second vertebra of Hesperomis regalis : 



Measurements of Twenty-second Vertebra. (No. 1200.) 



Length of centrum, 24. OP 



Least transverse diameter of centrum, 11.0 



Transverse diameters of anterior articulation of centrum, 17.0-24.0 



Vertical diameters of anterior articulation of centrum, 10.0-15.0 



Transverse diameters of posterior articulation of centrum, 15.5-24.0 



Vertical diameters of posterior articulation of centrum, 11.0-18.0 



Diameter of vertebra, across pre-zygapophyses, 22.0 



Diameter of vertebra, across parapophyses, 27.0 



Diameter of vertebra, across post-zygapophyses, 22.0 



Diameters of pre-zygapophyses, 9.0- 9.0 



Diameters of post-zygapophyses, 9.0-10.0 



Length of floor of neural canal, 25.5 



Length of roof of neural canal, 21.0 



Transverse diameter of neural canal, at anterior opening, 8.0 



Vertical diameter of neural canal, at anterior opening, 6.0 



Transverse diameter of neural canal, at posterior opening, 8.0 



Vertical diameter of neural canal, at posterior opening, 6.5 



Diameters of articulation for head of rib, 7.0- 7.5 



