AXIAL SKELETON OP THE STEUTHIONID^. 7 



much longer pre- and postaxially, while its postaxial excavation is very much smaller. 

 The central postaxial surface is medianly produced ventrad. The di- and parapophyses 

 are as in the twenty-first vertebra of StrutUo. The hypapophysis is smaller than in the 

 seventeenth vertebra, but extends preaxiad much beyond the preaxial surface of the 

 centrum. 



The nineteenth vertebra has the neural spine more pre- and postaxially, but not more 

 dorsally, extended than in the eighteenth vertebra. There are no fossae beside it. The 

 hypapophysis is very slightly produced. The diapophysial articular surface is placed 

 medianly on the transverse process. The posterior zygapophyses do not extend post- 

 axially beyond the centrum. 



The twentieth vertebra exhibits the trace of a hypapophysis at each end of the cen- 

 trum. It is very like its predecessors, the zyg-, di-, and parapophyses being of about 

 the same size and relative position. The neural spine is rather shorter pre- and post- 

 axially and a trifle higher. Its postaxial excavation is smaller. 



THE DOKSO-LUMBAR VERTEBE^. 



The twenty-first vertebra rather resembles the twenty-fourth of Struthio; but the 

 neural spine is much less high, even relatively. There is no trace of a hypapophysis 

 postaxially ; but there is a rudiment at the preaxial end of the centrum. The di- and 

 parapophysial articular surfaces are about as remote from each other as in the twentieth 

 vertebra. When the vertebra is viewed dorsally no radiating lamellae are to be seen, 

 thus differing from the twenty-fourth vertebra of Struthio. 



The twenty-second vertebra appears to answer to the twenty-fifth of Struthio, which 

 it greatly resembles, except that its neural spine is less high, though it is much longer 

 and more slender than in the preceding (twenty-first) vertebra. A vertical ridge 

 distinctly divides, medianly, the postaxial neural excavation. 



The twenty-third vertebra differs from its predecessor in that it is shorter pre- and 

 postaxially. Its neural spine is higher and more slender, the preaxial surface of its 

 centrum is less concave, and the di- and parapophysial articular surfaces are less remote 

 one from another. 



THE LUMBAR VERTEBRA. 



The twenty-fourth vertebra is the first postdorsal vertebra which has no distinct rib. 

 It appears to answer to the twenty-eighth of Struthio, but differs in that its neural spine 

 is not higher than its predecessor's, that its transverse processes incline preaxiad instead 

 of postaxiad, and that the neural arch is so cancellous and imperfectly ossified. 



