AXIAL SKELETON OF THE STRUTHIONID^. 51 



SUMMARY AND CONCLUSION. 



On reviewing the characters hereinbefore given, it will, I think, appear that the axial 

 skeleton of Drommus presents us with the least specialized and differentiated type, round 

 which, as it were, cluster the genera Casuarius, Apterijx, and Bimrnis, which all agree 

 with the Emu in differing from both Struthio and Ehea in the much less elongated 

 condition of their cervical vertebrae, as well as the greater ruggedness occasioned, in 

 those bones, by the great development of the various processes and the diapophysial 

 ridges. They also all differ from the two genera last named in the absence of either a 

 pubic or an ischiatic symphysis, and in the nearly equal projection postaxiad of ilium, 

 ischium, and pubis, all three. In these two latter characters the pelvis resembles the 

 undeveloped condition of the pelvis in the young of Struthio and Rhea. Again, the 

 four genera first named agree in not having more than one articular surface at the distal 

 end of each sternal rib, and in not having any prominence on the ventral surface of the 

 sternum. 



Again, it will, I think, be admitted that the genera Brommis and Casuarms seem, 

 thus considered, to be very closely allied, while Dinornis exhibits a considerable affinity 

 to Apteryx, although intermediate between the last-mentioned genus and Casuarius. 

 Thus the New-Zealand genera agree to differ from the others in the divergence post- 

 axially of the ischium and pubis from the ilium, in the considerable expansion of the 

 distal end of the ischium and the greater slendeiness of the pubis. They also differ 

 in that the supratrochanteric process is absent or inconspicuous, in the more ventral 

 situation of the acetabula in relation to the sacro-caudal vertebrae, as also in the excess 

 of the breadth of the sternum over its length, the minuter size of the coracoid-grooves 

 and their remoteness one from the other, as also in the presence of long median and 

 lateral xiphoid processes. 



Of the two genera Struthio and Bhea, the latter seems especially aberrant in the 

 abortion of the sacro-caudal vertebra;, and in carrying those characters in which the 

 cervical vertebra; generally of Struthio differ from the other Old-World forms to a still 

 greater degree. Thus, while Rhea seems the most aberrant genus in one direction 

 (judging, of course, from the axial skeleton only), Apteryx seems the most divergent in 

 another. 



These affmities seem to agree, in the main, with those pointed out by Professor 

 Garrod i, who represents Struthio and Rhea as agreeing to differ from the other existing 



' P. Z. S. 1874, p. 120. 



