18 MR. ST. GEOKGE UnVAET ON THE 



the interzygapophysial perforation minute. The postzygapophyses with their hyperapo- 

 physes extend more postaxiad than in either of the other genera. 



The ihird vertebra agrees in its proportions with that of Rhea, and differs from that 

 of Struthio, except that the styloid rib is relatively longer than even in Struthio. The 

 neural spine is excavated in front (slightly) as well as postaxially. The hyperapophyses 

 are more grooved dorsally than in Rhea, while the interzygapophysial foramen is larger 

 than that of the axis instead of smaller. The metapophyses are already marked. 



The fourth vertebra quite agrees with that of Rhea, except that the rib is longer, 

 and 'that the neural spine (as in Struthio) is so grooved both pre- and postaxially that 

 the median part is much reduced. The metapophyses are larger than in either of the 

 other genera. 



The fifth vertebra contrasts, as to length, less with the fourth than in Rhea, the 

 cervical vertebrse increasing more gradually in length, and never attaining such a rela- 

 tive development axially as in either of the other two genera. The transverse diameter 

 of the preaxial part still more exceeds that of the postaxial part than in Rhea ; the rib 

 is relatively much longer. The interzygapophysial ridge may or may not be perforated ; 

 but the metapophyses are more strongly marked than in the fourth vertebra. 



The sixth vertebra differs only slightly from the fifth in length. The neural arch 

 and spine assume the characters of those of the thirteenth cervical vertebra of Rhea. 

 The interzygapophysial ridge is only minutely perforated. The rib here, as throughout, 

 is longer than even in Struthio relatively to the axial extent of its supporting vertebra, 

 extending to, or beyond, the most preaxial part of the postaxial central articular sur- 

 face in all the cervical vertebrae. The metapophyses are still stronger ; and catapophyses 

 begin to appear ; and they diverge ventrad much less than in Rhea. 



The seventh vertebra presents similar characters to those of the sixth ; but the meta- 

 pophyses are again stronger, and the interzygapophysial ridge is large and perforated, 

 the lamella forming a canal which passes ventrad and postaxiad on each side of the 

 neural lamina. 



The following vertebrae, from the eighth to the eleventh, present characters similar to 

 those of the seventh ; only the neural spine grows somewhat longer, though being still 

 short and stumpy, even in the eleventh vertebra. 



In the twelfth vertebra the development of the neural spine is much like that of the 

 sixteenth vertebra of Struthio. From this vertebra postaxiad, the intei-zygapophysial 

 ridge may or may not be perforated. 



The vertebrae from the thirteenth to the seventeenth inclusive are all much more 

 alike than is the case in Rhea ; they gradually, however, become larger and more massive, 

 the neural spines rising very slightly. The catapophyses approximate together in the 

 seventeenth vertebra, still, however, remaining distinct, as do those of the last cervical 

 (fourteenth) vertebra of Rhea, and not uniting as in the last cervical (seventeenth) ver- 

 tebra of Struthio. 



