~ 
AXIAL SKELETON OF THE OSTRICH. 423 
Its centrum is shorter pre- and postaxially, and its yentral surface is concave trans- 
versely and very strongly so at each lateral margin. 
Its newral arch rests half on the postaxial part of the preceding centrum, half on the 
preaxial part of its own centrum ; it has a large intervertebral opening both pre- and 
postaxial of its ventral portion. 
The diapophysis is elongated and slender, ascends dorsal and slightly preaxiad and 
outwards, with a small external flattened facet at its extremity (fig. 59, 4). 
The parapophysis is formed in a minute degree by the most ventral point of the 
neural arch, but mainly and subequally by the adjacent portions of the centra which 
support the arch (fig. 59, p® & p*). 
The neural foramen of the centrum is larger. 
Tuer THIRTY-THIRD VERTEBRA. 
This vertebra (figs. 59, 60, & 61, 5) is similar to that last described; but the diapo- 
physis is shorter, the neural arch more antero-posteriorly extended at its ventral part. 
the intervertebral opening postaxial to it being much smaller. 
VENTRAL ASPECT OF LUMBAR AND SACRAL VERTEBRA OF AN IMMATURE SPECIMEN. 
(¥ natural size). 
Fig. 60. 
1-12. Centra of vertebrae from twenty-ninth to fortieth inclusive; d', diapophysis of twenty-ninth vertebra ; 
@, diapophysis of thirty-sixth vertebra; dp", diapophysis of thirty-ninth vertebra conjoined with its 
parapophysis ; p*, anterior parapophysial projection of thirty-second vertebra ; p* posterior parapophysial 
projection of the same vertebra ; p°, posterior parapophysial projection of thirty-third vertebra; p°, ante- 
rior parapophysial projection of thirty-fourth vertebra ; p*®"", conjoined parapophyses of thirty-sixth, thirty- 
seventh, and thirty-eighth vyertebre. The last of these three is anchylosed to its supporting centrum (10) ; 
but each of the two preceding capitula is united by suture, with a pair of slight parapophysial projections 
contributed by contiguous vertebrie. 
. 
There is a considerable defect of ossification in the neural arch (fig. 61,5) on each 
side of the spine, oval in shape and extending nearly from the spinous process to the 
diapophysis. 
The ventral surface of its centrum (fig. 60, 5) is slightly narrower antero-posteriorly, 
