34 ME. ST. GEOEaE MIVAET ON THE 



Compared with the axial skeleton of iJromceus, that of Casuarius has the cervical 

 vertebrae 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 vertebrae an irregularity of surface which contrasts strongly with the 

 relatively smooth elongated cervical vertebrae of Struthio and Rhea. 



Casuarius is, in fact, evidently closely allied to BromoBus ; and these two types are 

 less specialized than are the diverging eccentric forms Struthio and Bftea. 



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 Struthionidae, 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 vertebrae and one cervico-dorsal ; there are four 

 dorsal and also four dorso-lumbar vertebra ; to these succeed about eight lumbar and 

 three sacral vertebrae, followed by three sacral and nine or seven caudal ^. Thus there 

 are forty-five or forty-seven vertebrae in all ; and of these as many as twenty-four belong 

 to the first four categories. 



THE CERVICAL VERTEBRA. 



The genus Ajiteryx 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 Struthionidae. 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 axis is even more exceptional, through its relatively enormous hyperapophyses 

 and long neural spine, both processes relatively exceeding those of any other of the 

 Struthionidae. Indeed, in the hyperapophysis of the axis in Ajpteryx, diapophysial ele- 

 ments seem to be latent also, as may be seen by following the process postaxially through 



' See Tol. ii. p. 286, plates liv., Iv. ' Seven in A. oivenii and nine in A. australis. 



