AXIAL SKELETON OP THE STRFTHIONID^. 17 



THE AXIAL SKELETON OF BROMJEUS (figs. 12 & 13). 



In Dromceus there are seventeen or eighteen cervical and three or four cervico-dorsal 

 vertebrae ; there are three or four dorsal and but two dorso-lumbar vertebrae ; to these 

 succeed eight lumbar and three sacral vertebrae, followed by ten or eleven sacro-caudal 

 and eight or nine caudal vertebrae. Thus there are about fifty-four vertebrae in all ; and 

 of these as many as twenty-six or twenty-seven belong to the first four categories, thus 

 difi'ering from Bhea and agreeing with Struthio, as is also the case with the last 

 category (the caudal vertebree), which are, within one or two, as numerous as in the 

 African genus. 



THE CEEVICAL VEETEBRtE. 



ATLAS AND AXIS OF EMU (natural size). 

 Fig. 14. Fig. 15. 



Ay 



Fig. 14. Preaxial view of atlas ; v, foramen encloBed 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 Ehea, 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 Mhea. 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 axis 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 



VOL. X. — PAKT I. No. 3. — March, 1877. d 



