328 PROF. ST. GEORGE MIVART ON THE 
lumbo-sacral vertebre than is the case in any of the Struthionide, except Apterya and 
Dinornis. There are three or four! true lumbar vertebra. 
The TWENTY-THIRD VERTEBRA (or first true lumbar) resembles its serial predecessor, 
except that there are no costal articular surfaces, but the transverse process is smooth 
on its ventral surface, and the centrum is more flattened ventrally. 
The arch formed by the junction between the postaxially extended and dorsally 
curved parapophysial transverse process of this vertebr, and the similarly curved, but 
preaxially extended, parapophysial transverse process of the twenty-fourth vertebra has 
here become a presacral foramen. 
The TWENTY-FOURTH VERTEBRA is similar to the last described; but the centrum is 
smaller, and the parapophysial transverse process more expanded and flattened ventrally. 
Its presacral foramen is smaller. 
The TWENTY-FIFTH VERTEBRA is almost quite similar to the twenty-fourth. 
The TWENTY-SIXTH VERTEBRA differs from the last in having its transverse process free 
postaxially, and not uniting with any parapophysis of the twenty-seventh vertebra. 
The postaxial margin of the transverse process forms the most ventral portion of the 
preaxial margin of the great lateral acetabular fossa. The diapophysis ascends 
obliquely dorsad and slightly externad to the ilium, and is generally quite distinct from 
the parapophysis. 
The intervertebral foramen is medianly constricted antero-posteriorly so as to 
approximate to two superimposed foramina. 
Tue LuMBo-sacRAL VERTEBRA. 
These vertebr are three in number—namely, the TWENTY-SEVENTH, TWENTY-EIGHTH, 
and TWENTY-NINTH. 
These three intimately united vertebree have the ventral surfaces of their centra 
narrowing postaxiad and concave transversely; thus forming a continuous plate, antero- 
posteriorly grooved (Plate LIX. fig. 3). 
Their diapophyses ascend almost directly dorsad, the two more posterior on each 
side (viz. those of the twenty-eighth and twenty-ninth vertebre) being visible through 
the acetabula when the pelvis is viewed laterally (Plate LIX. fig. 2). 
There are no parapophyses, or only minute rudiments of such. The intervertebral 
foramen behind each vertebra is more or less median, constricted antero-posteriorly, 
Tue SacraL VERTEBRA. 
There are three sacral vertebre—the THIRTIETH, THIRTY-FIRST, and THIRTY-SECOND ; and 
they form a series, the centra of which decrease in size postaxially, and continue on 
1 Only in the specimens of P. mitratus, No. 70. 3. 30. 1, in the British Museum, have I found this number 
reduced to three, 
