AXIAL SKELETON OF THE STRUTHIONID. 35 
the cervical vertebre. 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 APTERYX (natural size). 
Fig. 29. Fig. 30. 

Fig. 29. Preaxial view of atlas. Fig. 30. Lateral view of atlas. 
Fig. 31. Lateral view of axis. 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 the fifth vertebra the separation is more easily to be traced; but in the sith 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, Dromeus, and Casuarius, is longest from about the sixth 
to the tenth vertebra, though from the sixth to the seventh in A. 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 vertebre. 
In the cervical vertebree postaxial to the sixth, each pleurapophysial lamella connect- 
FQ 
