AXIAL SKELETON OF THE OSTRICH. 



419 



or less coalesced by the abortion of the lamella running from the root of the diapophysis 

 to the parapophysis. 



The neural spine is swollen at its distal end, and is in length about twice the antero- 

 posterior extent of the whole vertebra. 



When the neural arch is viewed from above, there may be sometimes seen six fossse 

 (fig. 57,/"^,/^,/^), owing, when this is the case, to the complete subdivision of the median 

 postaxial fossa into two by the greater postaxial development of the postaxial margin 

 of the neural spine, which may extend to the postaxial margin of the neural arch. 



TWENTY-FIFTH VERTEBRA (i natural size). 



Pig. 55. Fig. 56. 



Fig. 57. 



Aspects. 



Fig. 54, lateral ; 55, preaxial ; 56, postaxial ; 57, dorsal (the neural spine being cut short off). 

 Letters as before, except /', antero-lateral fossa ; /-, lateral fossa ; /^, posterior fossa of neural arch. 



The degree of special development of this vertebra varies, however, with the more or 

 less preaxial extension of the ilia, also with the total number of vertebrae of which the 

 spinal column consists ; for there may be one less than the number herein given. 



The twenty-fifth vertebra supports a long rib (the eighth), which articulates with the 

 sixth sternal rib. 



3n2 



