AXIAL SKELETON OP THE STEUTHIONID.E. 39 



THE SACRAL VERTEBRA. 



The three sacral (the thirtij-third, thirty-fourth, and thirttj-fifth) vertebi-se are, iu 

 Apferyx, very distinct from both their preaxial predecessors and their postaxial suc- 

 cessors. Each sends out on each side a transverse process to abut against the post- 

 acetabular part of the ilium. 



THE SACRO-CAUDAL VERTEBRA. 

 The vertebrse of this category are fewer in number in Apteryx than in any other of 

 the Struthionidee, and are singularly compressed laterally. They are devoid of trans- 

 verse processes, and are chiefly remarkable for the peculiarity of" their position. Instead 

 of ascending, as in Rhea, these vertebrae descend ventrad to the postaxial parts of the 

 ilia. In spite of these, they are less ventrally extended between the acetabula than in 

 any except Shea ; so that when the pelvis is held horizontally with one of the acetabula 

 opposite the eye, about half the aperture of the acetabulum of the opposite side becomes 

 visible. The nearest approximation to this condition is that found in Casuariiis, though 

 considerably less of the opposite acetabulum can thus be seen in that genus. 



THE CAUDAL VERTEBRA. 



These vertebrae are from seven to nine in number — namely, seven in A. australis and 

 nine in A. owenii. Transverse processes are present in the third, fourth, and fifth 

 caudal vertebrae, especially in the two latter ; and these help to produce a broadening- 

 out of -the fourth and fifth or the fourth, fifth, and sixth caudal vertebrae; so that the 

 skeleton of the tail is wider towards its middle than it is either more pre- or more 

 postaxially. This is a character not similarly marked in any other genus of the 

 Struthionidae. 



The pygostyle is rather elongated, conical, irregular, and somewhat laterally com- 

 pressed and flattened ventrally. It looks like three or four- successively smaller and 

 smaller vertebrae ankylosed together. 



THE PELVIS. 



^ When viewed preaxially the pehds is remarkable for the much greater divergence of 

 the ilia, which form together a much more obtuse angle than in any other of the 

 Struthionidae. It is also remarkable for the much greater visibility of the ischia and 

 pubes (owing to their extreme descent postaxially), and for the relatively much longer 

 last rib. 



Viewed postaxially the same peculiarities are noticeable, as also the postaxial descent 

 of the ilia (which is much as in Casuarius), and the absence of supratrochanteric 

 processes. The ilia are very much flattened against the postacetabular vertebite 

 included between them. 



Viewed laterally, the slenderness of the pubis and breadth of the ischium are remark- 



