350 PROF. ST. GEORGE MIVART ON THE 
vertebra—the THIRTY-FIRST and the THIRTY-SECOND,—although there may be as many as 
three, or sometimes, apparently, but one. 
Tue SacrkaAL VERTEBR&E. 
Of these there are at most but two, the THIRTY-THIRD and the THIRTY-FOURTH. 
They differ from those of Sula in that, though the first has, like that of Sula, its 
parapophysis detached from more dorsal ossification, that of the second (thirty-fourth 
vertebra) often, if not generally, has its parapophysis continuously ossified with what is 
dorsal to it, so as to constitute a little subvertical sheet of bone formed of parapophysis 
and diapophysis conjoined (Plate LXI. fig. 1). 
Tue SAcko-cauDAL VERTEBRA. 
These are seven or eight in number, from the THIRTY-FIFTH to the FORTY-SECOND 
inclusive (Plate LXI. fig. 1). The condition of their parapophyses is generally inter- 
mediate between Pelecanus and Sula, not even arising so ventrally as in the former and 
not generally bent up dorsad so suddenly as in the latter, except in the thirty-fifth 
vertebra, where they are quite so. ‘Their general appearance, however, is more like 
that presented by Sula than by Pelecanus. They are subequally developed as to the 
transverse extent of their parapophyses ; and the last two considerably increase in antero- 
posterior extent. 
Tur CauDAL VERTEBRA. 
These vertebra, from five to eight in number, rapidly increase in transverse diameter ; 
and the second may have a hypapophysis, while the third has generally a distinctly 
bifurcating hypapophysis, which becomes much larger in the succeeding two vertebrae. 
Each vertebra has a pair of small zygapophyses (Plate LXI. fig. 5), 
The PYGOSTYLE is very different in shape from that of either Pelecanus or Sula. It 
is much shorter and sharply bent up dorsad upon the free caudals; its ventro-postaxial 
margin is gently concave, and its dorso-preaxial one gently convexo-concave postaxiad— 
both as in Sula; but it is a very much shorter bone, and may even approximate in 
outline to an equilateral triangle, though it may be a triangle of which the breadth is 
but half the length, 
Tue PELvis, 
This includes as many as from fifteen to seventeen vertebra. It more nearly resembles 
that of Sula than that of Pelecanus, but is more elongated antero-posteriorly. 
Viewed Jaterally it agrees with Sula, and differs from Pelecanus in the points men- 
tioned in describing Sula, except that the sacro-iliac ankylosis is longer, and the ilio- 
caudal spine is a very long pointed process (Plate LX. fig. 6). 
Compared with Swla, the sciatic foramen is more pointed postaxially, and, as in 
