AXIAL SKELETON OF THE STEUTHIONID.E. 



35 



the cervical vertebrae. There is also a small and rudimentary parapophysial process ( p) 

 on each side of the axis, projecting from about the postaxial end of the preaxial third 

 of the outer surface of that bone. The axis has no hypapophysial process. 



ATLAS AND AXIS OF APTEETX (natural size). 



Fis;. 29. 



Fig. 30. 



Fig. 31 



Fig. 29. Preaxial view of atlas. 

 Fig. 31. Lateral view of axis. 



Fig. 30. Lateral view of atlas. 

 Fig. 32. Ventral view of axis. 



The third vertebra has a high neural spine and is the first to exhibit catapophyses. 

 It has the hyper- and diapophyses still blended as in the axis ; but in the fourth 

 vertebra (which also has a high neural spine) traces may be detected of a separation 

 between the hyperapophysial and diapophysial elements (fig. 34, d & hp). 



In t\ie fifth vertebra the separation is more easily to be traced; but in the sixth ver- 

 tebra they have completely separated, the hyperapophyses becoming approximated to 

 the postaxial part of the neural spine, and the diapophysis (containing also probably a 

 latent metapophysis) beginning to stand out almost like an upper rib, approximating in 

 length and projection postaxiad to the styloid rib, which projects postaxially ventrad from 

 the more ventral portion of the same vertebra. This parapophysial rib, which answers 

 to the styloid ribs of Struthio, Dromceus, and Casuarius, is longest from about the sixth 

 to the tenth vertebra, though from the sixth to the seventh in /I. australis, and from 

 the sixth to the tenth inclusively in A. owenii, the diapophysis (the upper rib) in each 

 vertebra surpasses in length its normal cervical rib. 



The neural spine, which was still long in the fifth vertebra, becomes short in more 

 postaxial vertebrse. 



In the cervical vertebrse postaxial to the sixth, each pleurapophysial lamella connect- 



f2 



