34 MR. ST. GEORGE MIVART ON THE 
Compared with the axial skeleton of Dromeus, that of Casuarius has the cervical 
vertebre shorter, axially, and has the catapophyses, hyperapophyses, and metapophyses 
more strongly developed, and making their appearance nearer to the preaxial end of 
the vertebral column. These various processes, together with the marked diapophysial 
ridges, give to the vertebra an irregularity of surface which contrasts strongly with the 
relatively smooth elongated cervical vertebre of Struthio and Khea. 
Casuarius is, in fact, evidently closely allied to Dromewus; and these two types are 
less specialized than are the diverging eccentric forms Struthio and Rhea. 


THE AXIAL SKELETON OF APTERYX. 
The axial skeleton of Apteryx is so very distinct and different in form as well as in 
size from that of the other Struthionide, that much detail may be dispensed with. 
This is still more the case on account of the elaborate description and figures of the 
skeleton of this genus which have already been given in the ‘Transactions’ of the 
Zoological Society’. 
In Apteryx there are fifteen cervical vertebre and one cervico-dorsal; there are four 
dorsal and also four dorso-lumbar vertebre; to these succeed about eight lumbar and 
three sacral vertebra, followed by three sacral and nine or seven caudal’. ‘Thus there 
are forty-five or forty-seven vertebrie in all; and of these as many as twenty-four belong 
to the first four categories. 
THE CERVICAL VERTEBRA. 
The genus Apteryax differs from all the preceding genera in the greater relative 
stoutness of the neck and production of its processes. 
The atlas is exceptional in that the preaxial articular surface of its centrum is scarcely 
at all notched dorsally. It is also remarkable for its very long hyperapophyses. It 
has no neural spine any more than any other of the Struthionide. ‘Transverse processes 
may be absent; or there may be a minute parapophysial process on each side. A rudi- 
mentary hypapophysial process may also be developed from the postaxial end of the 
ventral surface of the atlas. 
The avis is even more exceptional, through its relatively enormous hyperapophyses 
and long neural spine, both processes relatively exceeding those of any other of the 
Struthionide. Indeed, in the hyperapophysis of the axis in Apteryx, diapophysial ele- 
ments seem to be latent also, as may be seen by following the process postaxially through 
1 See vol. ii. p. 286, plates liv., lv. * Seven in A, owenti and nine in A, australis. 
