AXIAL SKELETON OF THE STEUTHIONID^. 19 



THE CEEVICO-DOESAL VERTEBK^. 



The eighteenth vertebra is like the first cervico-dorsal (fifteenth) of Ehea, except that 

 the preaxial central surface is not nearly divided medianly, and that the postaxial central 

 surface does not diverge ventrad, the ventral margin being scarcely at all concave, though 

 more in excess of the dorsal margin than in Struthio, while the degi-ee to which it is 

 visible in profile is also intermediate. The hypapophysis bifurcates distally, though 

 having a single root. It does not extend so much ventrad, relatively, as in Bhea. The 

 rib may be rather more or rather less developed than in the preceding vertebra. It 

 may, in the adult condition (as e. g. in No. 1358), be unankylosed. The prajzygapo- 

 physes exceed the preaxial extension of the parapophyses more than in Struthio, and 

 much more than in Mea. The neural spine is not dorsally grooved, but is excavated 

 both pre- and postaxiaUy. 



The nineteenth vertebra, compared with the sixteenth of Shea, has the postaxial 

 surface of its centrum less diiferent from its predecessor ; yet its ventral does not so much 

 exceed its dorsal margin. The hypapophysis is much more like that of Struthio than 

 that of Bhea. The neural spine is not grooved dorsally. The diapophysis is more 

 axially extended. The parapophysial articular surface is deeper and more dorso-ventrally 

 extended ; and that of the diapophysis is also rather more concave. 



The twentieth vertebra has its hypapophysis more like that of Struthio than that of 

 Bhea, although, as in the last-mentioned genus, it extends much postaxiad. The trans- 

 verse processes are more axially extended, and the neural spine is smaller, than in 

 Bheas seventeenth vertebra, which this one otherwise much resembles. 



The twenty-first vertebra has its hypapophysis as large as that of the twentieth ver- 

 tebra, except when (as in No. 1358) an extra intercalated vertebra alters the relations. 

 The transverse process is rather more, and the neural spine rather less extended axially. 

 The postaxial excavation of the neural spine is less in defect of that of the preceding 

 vertebra than in Bhea ; otherwise the characters of this vertebra are much like those 

 of the first dorsal vertebra in that genus. As in Struthio, there is a pit on each side 

 of the preaxial surface of the neural spine. This pit is serially homologous with the 

 interzygapophysial canal. 



THE DOESAL VEETEBRiE. 

 The twenty-second vertebra has a very small hypapophysis, though a larger one than 

 in the other two genera. The diapophysial articular surface is preaxiad to the middle 

 of the transverse process. The neural spine is not so axially extended as in the pre- 

 ceding vertebra, but more dorsally. There is a deep fossa on each side of the preaxial 

 surface of the neural spine. The postzygapophyses do not extend postaxiad of the 



centrum. 



The tioenty-third vertebra has no hypapophysis at either end of its centrum. The 



d2 



