18 MR. ST. GEORGE MIVART ON THE 
the interzygapophysial perforation minute. The postzygapophyses with their hyperapo- 
physes extend more postaxiad than in either of the other genera. 
The third 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 jifth vertebra contrasts, as to length, less with the fourth than in Rhea, the 
cervical vertebrae 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 sivth 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 vertebra, 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 interzygapophysial 
ridge may or may not be perforated. 
The vertebree 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. 
