2G ODONTORNITIIES. 



directed outward, backward and downward, and situated below the upper 

 portion of the posterior articulation. 



The ventral surface of this A^ertebra is excavated behind the anterior 

 articular face, and between the ridges on the opposite sides of the centrum. 

 This excavation, however, is less pronounced than in the fifth vertebra, and 

 has no definite posterior limit ; but the depression continues through the 

 whole length of the vertebra, nearly disappearing a little behind the middle 

 of the centrum, and becoming again deeper posteriorly. The tubercle upon 

 the upper part of the lamina enclosing- the lateral foramen is larger and 

 more prominent than in the fifth vertebra, and is situated farther from the 

 pre-zygapophysis. It represents the diapophysis, and attains its full 

 development in the dorsal vertebrae. The lateral foramen is larger than in 

 the fifth vertebra. In the specimen from which the figures are mostly 

 drawn, this vertebra is united to the following one by the matrix, and hence 

 its posterior articular face is not exposed. ' The neural arch, also, is crushed, 

 and the dotted outline of the neural spine is drawn from another specimen 



The dimensions of the sixth vertebra of Hesperornis regalis here 

 recorded include those of the type specimen, number 1200, and two others, 

 both well preserved. 



Measurements of Sixth Vertebra. (No. 1200.) 



Length of centrum, . ._ 29.0 mra 



Transverse diameters of anterior articulation of centrum, 1 2.0-15.0 



Vertical diameters of anterior articulation of centrum, .. 6.0-10.0 



Transverse diameters of posterior articulation of centrum, .. 10.0-14.0 



Vertical diameters of posterior articulation of centrum, 8.5-11.0 



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



Transverse diameter of vertebra, across diapophyses,.. 25.0 



Transverse diameter of vertebra, across pleurapophyses, at base,.. .-. 21.0 



Diameters of pre-zygapophyses, 6.5- 9.8 



Length of floor of neural canal, 30.0 



Vertical diameter of lateral foramen, 5.5 



Transverse diameter of lateral foramen, _ 3.0 



Measurements. (No. 1206.) 



Length of centrum, .._ . ._ 1 3] .0 ram 



Transverse diameters of anterior articulation of centrum, 10.0-1 2.0 



Vertical diameters of anterior articulation of centrum, ..._ 6.0- 9.0 



Transverse diameters of posterior articulation of centrum,, . . _• 10.0-16.0 



