DORSAL VERTEBRAE OF HESPERORNIS. 47 



The Nineteenth Vertebra. (Plate V, figure 3.) 



The nineteenth vertebra is slightly longer than the eighteenth, and 

 has a somewhat stouter centrum. The latter is as broadly, but rather less 

 deeply, excavated at the sides, and was provided with a less powerful hypa- 

 pophysis, which, however, is not preserved in the specimen figured. The 

 articular surface for the head of the rib is a little higher on the side of the 

 vertebra, and supported upon a rather less prominent parapophysis. The 

 diapophyses, as in the preceding vertebra, point somewhat diagonally 

 upward, and backward. They are grooved, especially near the base in 

 front, and preceded by a much smaller and shallower pit than in the 

 eighteenth vertebra. The depression behind the diapophysis is nearly as 

 in that vertebra. The neural spine expands more antero-posteriorly at the 

 top than in the eighteenth vertebra, and there is a somewhat larger fossa 

 behind its base. The zygapophyses are similar to those in that vertebra. 



Measurements of the nineteenth vertebra in Hesperornis regalis, taken 

 from three specimens, will be found below : 



Measurements of Nineteenth Vertebra. (No. 1207.) 



Length of centrum, 24.'0 mm 



Transverse diameters of anterior articulation of centrum, 16.5-23.0 



Vertical diameters of anterior articulation of centrum, 9.0-12.0 



Transverse diameters of posterior articulation of centrum, 13.5-22.0 



Vertical diameters of posterior articulation of centrum, 10.0-14.5 



Transverse diameter of vertebra, across pre-zygapophyses, , 21.0 



Transverse diameter of vertebra, across diapophyses, 61.0 



'Transverse diameter of vertebra, across post-zygapophyses, 19.0 



Diameters of pre-zygapophyses, 10.0- 7.0 



Diameters of post-zygapophyses, 10.0- 8.0 



Length of floor of neural canal, 25.5 



Length of roof of neural canal, 23.0 



Transverse diameter of neural canal, at anterior opening, 8.0 



Vertical diameter of neural canal, at anterior opening, 6.5 



Transverse diameter of neural canal, at posterior opening, 7.5 



Vertical diameter of neural canal, at posterior opening, 7.0 



Diameters of articulation for head of rib, 8.0- 6.2 



Diameter of articulation for tubercle of rib, 7.5 



Height of neural spine above floor of neural canal, 33.0 



Antero-posterior diameter of neural spine, — 23.0 



