178 PEOPESSOE OWEN ON THE GENUS DINOENIS. 



In Dinornis the twenty-fourth vertebra (3rd sacral), answering to the twenty-eighth 

 vertebra of Struthio (Mivart's ' lumbar vertebra '), differs in presenting an unmistakably 

 rib-like pleurapophysis, although unanchylosed. The fourth sacral in Dinornis is the 

 first which may be said to " present no indication of a rib," and which would be entitled 

 to the term " lumbar," according to such character. I view, however, the parapophysial 

 element of this transverse process as more probably the serial homologue of the cervical 

 part of the preceding pleurapophysis. 



With this explanation the neural arch of the fifth sacral vertebra in Dinornis, as in 

 Struthio, advances and crosses the interspace between its own and the preceding cen- 

 trum; and the thirteenth vertebra is that in which the arch resumes its normal con- 

 nexions. Thus the interlocked part of the sacrum in Dinornis is more extensive than 

 in Struthio, and relates to the heavier mass which the pelvis had to transmit upon the 

 femora. 



The antacetabular part of the sacrum (1st to 6th vertebra in Dinornis) is relatively 

 shorter and broader than in Struthio ; the postacetabular part is still broader in pro- 

 portion to its length ; and this part is shorter than the antacetabular part, instead of 

 being, as in Struthio, longer. 



More striking difi'erences are presented by the pelvis as a whole. The antacetabular 

 part of the ischium is relatively longer ; the postacetabular part is shorter, but much 

 broader in Dinornis than in Struthio : the greater relative breadth of the entire pelvis 

 would seem to relate to the larger proportional size of the egg in Dinornis. 



The ischium is shorter and deeper than in Struthio : it unites with the ilium 

 anteriorly to bound there the ischiadic notch, which remains open posteriorly, as in 

 Struthio, and is not circumscribed by a second terminal union of the ischium with 

 the ilium, as in Dromaius. The obturator interspace, closed behind, as in Struthio, by 

 ischial confluence with the pubis, and having its fore part defined by the descending 

 process of the ischium, is much narrower in Dinornis, as in Apteryx. The pubis does 

 not send oflF so long and well-defined a ' pectineal process ' ^, as in Struthio ; its body 

 extends backward parallel with the ischium, slightly concave downward, and ter- 

 minates in the vertical expansion joining the ischium without being continued down- 

 ward and forward to meet its fellow at the symphysis, a structure which is peculiar, 

 among birds, to the genus Struthio. 



The type of the pelvis in Dinornis is that of the Apteryx, not of the Emu or Cas- 

 sowaiy ; it differs therefrom in less marked modifications than from the pelvis in 

 Struthio and Bhea. 



The number of terminal sacral vertebrae in Dinornis maximus, answering to those 

 defined as ' sacro-caudals' ^, is four. The last of these in Dinornis is the thirty-ninth of 

 the vertebral series ; in Struthio it is the forty-sixth. . 



' For this process in Apteryx australis, see Trans. Zool. Soc. vol. ii. p. 291. In the two skeletons of the 

 smaller Kivi {Apteryx Owenii, Gd.) I have found ossification extending along the ligament attaching the 

 pectineal process to the last sacral rib. ^ myart, ut sup>rci, p. 426, fig. 62. 



