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 Dromeus presents us with the least specialized and differentiated type, round 
which, as it were, cluster the genera Casuarius, Apteryx, and Dinornis, which all agree 
with the Emu in differing from both Struthio and Rhea in the much less elongated 
condition of their cervical vertebra, 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 Khea. 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 Dromeus and Casuarius seem, 
thus considered, to be very closely allied, while Dinornis exhibits a considerable affinity 
to Apteryx, although intermediate between the last-mentioned genus and Caswarius. 
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 slenderness 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 vertebre, 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 Rhea, the latter seems especially aberrant in the 
abortion of the sacro-caudal vertebr, and in carrying those characters in which the 
cervical vertebrae 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 affinities seem to agree, in the main, with those pvinted out by Professor 
Garrod 1, who represents Struthio and Rhea as agreeing to differ from the other existing 
1 P. ZS. 1874, p. 120. 
