AXIAL SKELETON OF THE OSTRICH. 



423 



Its centrum is shorter pre- and postaxially, and its ventral surface is concave trans- 

 versely and very strongly so at each lateral margin. 



Its neural arch rests half on the postaxial part of the preceding centrum, half on the 

 preaxial part of its own centrum ; it has a large intervertebral opening both pre- and 

 postaxial of its ventral portion. 



The diapojihysis is elongated and slender, ascends dorsal and slightly preaxiad and 

 outwards, with a small external flattened facet at its extremity (fig. 59, 4). 



The parapophijsis is formed in a minute degi'ee by the most ventral point of the 

 neural arch, but mainly and subequally by the adjacent portions of the centra which 

 support the arch (fig. 59,^^' &^*). 



The neural foramen of the centmm is larger. 



The Tiiikty-thied Vertebra. 

 This vertebra (figs. 59, 60, & 61, 5) is similar to that last described ; but the diapo- 

 physis is shorter, the neural arch more antero-posteriorly extended at its ventral part, 

 the intervertebral opening postaxial to it being much smaller. 



VENTRAL ASPECT OF LUMRAR AND SACRAL VERTEBRA OF AN IMMATURE SPECIMEN. 



(I natural size). 

 Fig. GO. 



1-12. Centra of vertebrae from twenty-ninth to fortieth inclusive; d\ diapophysis of twenty-ninth vertebra ; 

 fZ', diapophysis of thirty-sixth vertebra; rfp", diapophjsis of thirty-ninth vertebra conjoined with its 

 parapophysis ; p'', anterior parapophysial projection of thirty-second vertebra : p^' posterior parapophysial 

 projection of the same vertebra ; p^, posterior parapophysial projection of thirty-third vertebra ; p'', ante- 

 rior parapophysial projection of thirty-fourth vertebra ; p^^'"', conjoined parapophyaes of thirty-sixth, thirty- 

 seventh, and thirty-eighth vertebrce. The last of these three is anchylosed to its supporting centrum (10) ; 

 but each of the two preceding capitula is united by suture, with a pair of slight parapophysial projections 

 contributed by contiguous vertebrse. 



There is a considerable defect of ossification in the neural arch (fig. 61, 5) on each 

 side of the spine, oval in shape and extending nearly from the spinous process to the 

 diapophysis. 



The ventral surface of its centrum (fig. 60, 5) is slightly narrower antero-posteriorly, 



