6 ME. ST. GEORGE MIVART ON THE 



The thirteenth vertebra may be compared with the fifteenth of Struthio. The most 

 noticeable differences are the still rudimentary condition of the styloid rib, the forked 

 central postaxial surface, and the decided extension of the pleurapophysis preaxiad of 

 the prcezygapophysis. This vertebra is hardly less extended pre- and postaxially than is 

 the twelfth vertebra ; and its proportions are more slender than in Struthio. 



The fourteenth vertebra, if compared with the sixteenth of Struthio, differs in that 

 the ventral surface of the centrum is not of increased -width, and that the styliform rib 

 (though still very small) is rather more instead of less developed than is its preaxial 

 predecessor. There is no trace of a hypapophysial ridge. The pleurapophysis still 

 extends preaxially beyond the praezygapophysis. 



THE CERVICO-DORSAL VERTEBRA. 



Vas, fifteenth vertebra agrees with the eighteenth of Struthio, except that its preaxial 

 central articular surface is almost divided into two lateral surfaces. The postaxial 

 central surface widely diverges ventrally, and (as in the fourteenth vertebra) exhibits 

 half its extent when the vertebra is laterally viewed. There is a hypapophysis, which 

 springs from a single root, but tends to bifurcate laterally. The ribs are more developed 

 than in any of the cervical vertebrae ; they still extend preaxiad of the praezygapophyses. 

 There is no true neural spine, the neural laminae being medianly grooved pre- and post- 

 axially. 



The sixteenth vertebra, which may be taken as equivalent to the nineteenth of 

 Struthio, is but very slightly larger than the fifteenth. The postaxial articular surface 

 of the centrum differs greatly from that of its predecessor, there being no diverging 

 ventral extensions, and its ventral margin being almost convex. The hypapophysis is 

 relatively larger than in Struthio, extending the whole length of the ventral surface. 

 It is much more inclined preaxiad, and both relatively and absolutely more extended 

 ventrad. The neural spine may be said to bifurcate laterally, there being a deep median 

 pre- and postaxial groove, thus differing greatly from the same part in Struthio. 



The seventeenth vertebra has a hypapophysis somewhat larger relatively than the 

 hypapophysis of the twentieth vertebra of Struthio. There is a stumpy neural spine, 

 the preaxial surface of which is nearly vertical. The postzygapophyses are not entirely 

 postaxial to the centrum. The praezygapophyses are hardly less extended laterally than 

 in the sixteenth vertebra. 



THE DORSAL VERTEBRA. 



The eighteenth vertebra differs from its predecessor much as the twenty-first of 

 Struthio differs from its two predecessors. The neural spine is at once higher and 



