AXIAL SKELETON OF THE PELECANIDA. 549 
processes. The centrum is more laterally compressed than in Sula; and there is a ridge 
running antero-posteriorly on each side of the origin of the hypapophysis. 
The TWENTIETH VERTEBRA is like the nineteenth of Sula, except that it has become 
distinctly opisthoceelous (fig. 36), and that there is a long hypapophysis, that it is 
still more compressed laterally, and has no marked antero-posterior ridge on each 
side of it. 
Tue Dorsal VERTEBRA. 
These are much more compressed laterally than in Sula or Pelecanus. 
The TWENTY-FIRST VERTEBRA (Plate LVII. figs. 37-39) has on its preaxial articular 
surface a median tract (of about one third of its total width) convex in both directions, 
and external to this, on each side, a tract which is concave from within outwards, Its 
postaxial articular surface is more simply and entirely concave than is that of the 
twentieth vertebra. There is a long hypapophysis, a little antero-posteriorly expanded 
at its distal end. This and the succeeding dorsal vertebre have styliform ossifications 
of tendon attached to the dorsum of the distal part of their transverse processes; and 
the neural spines are, to a less extent, similarly affected. 
The TWENTY-SECOND and TWENTY-THIRD VERTEBRA (Plate LVII. figs. 40-45) are simply 
conyex in front, centrally, and concave behind, each surface being much more dorso- 
ventrally than transversely extended. The hypapophyses are nearly as in the twenty- 
first vertebra. 
The TWENTY-FOURTH VERTEBRA is the first to form part of the ankylosed pelvic mass; 
its preaxial surface is like that of its serial predecessor, except that it is somewhat 
broader. The hypapophysis is slightly smaller (Plate LX. fig. 6, XXIV). 
The TWENTY-FIFTH VERTEBRA is like its predecessor, but is smaller, more compressed, 
and with a smaller hypapophysis. Generally the hypapophysis of this vertebra is (like 
its three serial predecessors) distinctly flattened ventrally; but it may not be so, and 
may be quite rudimentary, as in the smaller skeletons in the British Museum, 68. 8. 
16. 3. 56. 11. 14. 17 and 66. 3. 28. 17. 
Tue Lumpar VERTEBRA. 
The TWENTY-SIXTH, TWENTY-SEVENTH, TWENTY-EIGHTH, TWENTY-NINTH, and THIRTIETH 
VERTEBR& resemble the lumbar vertebre of Sula, save in their greater number, the 
presence of distinct hypapophyses to the first two, and the presence, generally, of three 
presacral foramina on each side, produced by the distal junction of the parapophyses of 
the four most postaxial lumbar vertebre; there may, however, be as many as four 
presacral foramina. 
Tue LumsBo-SacRAL VERTEBRE. 
From the intervertebral foramina there appear generally to be two lumbo-sacral 
3B 2 
