316 PROF, ST. GEORGE MIVART ON THE 
These vertebre may be subdivided as follows—16 cervical, 1 cervico-dorsal', 5 dorsal, 
4 lumbar, 3 lumbo-sacral’, 3 sacral, 4 sacro-caudal®, and 6 caudal, besides the pygostyle. 
The whole axial skeleton is exceedingly pneumatic, each vertebra being very light, 
and having a swollen appearance with smooth surfaces and ridges, and processes but 
little developed. Hyperapophyses and metapophyses are small; and only three or four 
vertebre have conspicuous hypapophyses. 
Besides the cervical vertebre, the two following ones are also generally movable. 
The rest of the dorsal vertebra and the lumbar vertebre have their bodies ankylosed 
together, and somewhat compressed laterally, but not remarkably so. 
Tur CrervicAL VERTEBRA. 
The cervical vertebre unite so as to form angles with one another, open ventrad till the 
seventh’s junction with the eighth, which forms an angle open dorsad, as does that of the 
eighth with the ninth, and so postaxiad till they unite without forming an angle at all. 
The ATLAS, compared with that of Struthio, is narrower transversely in proportion to 
its antero-posterior extent (Plate LV. figs. 1 & 2). 
Viewed preazially, the dorsum of the neural arch is more visible, because its pre- 
axial part is more inclined ventrad. The odontoid notch is relatively deeper, and has 
the minute secondary notch on the middle of its dorsal margin more marked. The 
dorsal ends of the preaxial articular surface are produced more preaxiad, and rise 
dorsad slightly above the level of the outward process, which they embrace. ‘There is 
no diapophysis. 
Postasxially, the ventral surface of the neural arch is more visible for the reason above 
given; the odontoid notch is deeper; and the articular surface of centrum is more 
curved, but scarcely at all produced preaxially on the neural surface of the centrum. 
Ventrally, there are either no catapophyses (or lateral hypapophysial processes), or 
they are quite minute, while the median hypapophysis is less produced postaxiad 
relatively than in Struthio. 
Viewed laterally, the preaxial margin of the pedicel of the neural arch is very 
slightly concave, while its postaxial margin is almost as concave as in Struthio. There 
are no hyperapophyses; and the zygapophyses are very small and inconspicuous. 
The preaxial margin of the centrum is more concave than in Struthio, on account of the 
greater production preaxiad of the dorsal parts of the preaxial central articular surface. 
Seen dorsally, the postaxial margin of the neural arch is less concave than in Struthio, 
on account of the less postaxiad production of the zygapophyses. 
The pedicels of the neural arch are very slender. 
The axis is inclined more dorsad postaxially upon the atlas than in Struthio; it is 
1 With movable ribs which do not reach the sternum, and with no lateral vertebral canal. 
? The pelvic vertebree without parapophyses. 
3 Postsacral vertebre forming part of pelvic mass. Sometimes there are but three of these. 
