AXIAL SKELETON OF THE STRUTHIONID. 17 
THE AXIAL SKELETON OF DROILAUS (figs. 12 & 13). 
In Dromeus there are seventeen or eighteen cervical and three or four cervico-dorsal 
vertebre ; there are three or four dorsal and but two dorso-lumbar vertebre; to these 
succeed eight lumbar and three sacral vertebra, followed by ten or eleven sacro-caudal 
and eight or nine caudal vertebrez. Thus there are about fifty-four vertebre in all; and 
of these as many as twenty-six or twenty-seven belong to the first four categories, thus 
differing from Rhea and agreeing with Struthio, as is also the case with the last 
category (the caudal vertebra), which are, within one or two, as numerous as in’ the 
African genus, 
THE CERVICAL VERTEBRA. 
ATLAS AND AXIS OF EMU (natural size). 
Fig. 14. Fig. 15. 

Fig. 14. Preaxial view of atlas; v, foramen enclosed by costal spiculum. Fig. 15. Lateral view of axis. 
Here and subsequently the letters refer to the same parts as in the corresponding illustrations of Rhea, except 
where differences are specified. 
The atlas differs from that of Struthio as does that of Rhea, except that the median 
dorsal notch is larger, that there is no hypapophysis, and that there is a costal spiculum 
on either side. The neural arch is somewhat more axially extended than in either of 
the other genera ; and the diapophyses are even smaller than in Rhea. The dorso-ventral 
height of the whole bone, compared with its breadth, is intermediate between that 
existing in the other genera, though more like that of Rhea. 
The aais exceeds the atlas in axial length still less than it does in Rhea; and its 
relative dorso-ventral extent is yet greater. There is also no hypodontoid pit for a liga- 
ment. The postaxial central surface is still more prolonged ventrad by the relatively 
still longer hypapophysis, which is vertically grooved at its root postaxially, and extends 
quite to the preaxial margin of the centrum, where it extends still further ventrad 
and quite as suddenly. The neural spine is relatively as well as absolutely shorter 
(axially) and may be higher than in Rhea; but the pneumatic foramen is smaller, and 
vou. X.—PArT I. No. 3.—March, 1877. ae 7 D 
