PRESACRAL VERTEBRAE OF ICHTHYORNIS. 135 



Transverse diameter of vertebra, across pre-zygapophyses, 1.5""" 



Transverse diameter of vertebra, across post-zygapophyses, 7.0 



Vertical diameter of neural canal, 2.2 



Transverse diameter of neural canal, 2.0 



Greatest diameter of lateral foramen, 2.5 



Least transverse diameter of centrum, 1.5 



The Fifteenth (!) Vertebra. (Plate XXVII, figure 4.) 

 A rather jDoorly preserved vertebra (number 1733) corresixmds imper- 

 fectly with the fifteenth vertebra of Sterna regia, with which it may be 

 compared. The centrum is constricted medially, but expands at each end 

 to support the articular faces, both of which are sub-circular, and very 

 slightly concave. The posterior face is rather deeper than the anterior, 

 which is somewhat inclined, so as to look a little downward and forward. 

 Beneath the anterior face, is a triangular area, with a small tubercle at each 

 of the upper external angles. Below, the centrum is continued downward 

 into a thin hypapophysis, the base of which does not extend backward on 

 the centrum quite to the posterior end. Above, on each side is a large oval 

 pneumatic foramen. The articular surface to receive the head of the rib 

 is situated near the base of the lateral wall of the neural canal. The 

 diapophysial articular surface for the tubercle of the rib is broken oif. 



The pre-zygapophyses are elongate, and look nearly directly upward, 

 and somewhat inward. They are considerably farther apart than the post- 

 zygapophyses, the difference being rather greater than in the corresponding- 

 vertebra of the Tern. The post-zygapophyses are imperfectly preserved 

 in this specimen, but appear to be shorter than the pre-zygapophyses. 

 The neural spine is absent, having been entirely broken away, so as to 

 expose the neural canal. 



This vertebra of Ichtliyornis victor has the following dimensions : 



Measurements of Fifteenth (?) Vertebra. (No. 1733.) 



Length of centrum, 5.6 mm 



Transverse diameter of anterior articulation of centrum, 3.5 



Vertical diameter of anterior articulation of centrum, 3.0 



Transverse diameter of posterior articulation of centrum, 3.0 



Vertical diameter of posterior articulation of centrum, 2.6 



Transverse diameter of vertebra, across pre-zygapophyses, 8.0 



Transverse diameter of vertebra, across post-zygapophyses, G.2 



