AXIAL SKELETON OF THE PELECANIDZ. 355 
ridges :—one median, hypapophysial ridge, extending to about the postaxial end of the 
preaxial two thirds of that surface ; and two lateral, parapophysial ridges (fig. 4, hy’), ex- 
tending and diverging postaxiad till each ends in a process on the ventral side of the ex- 
ternal ventral angle of the postaxial articular surface of the centrum. There thus comes 
to be a small fossa beneath the postaxial third of the centrum. The postzygapophyses 
project postaxiad much beyond the postaxial end of the centrum, 
In Plotus nove-hollandie the hypapophysial ridge is more developed, and extends 
almost to the postaxial end of the centrum, while the lateral ridges are like delicate 
rib-like styloid processes, there being a defect of ossification in each. 
The TuirD verTEBRA (Plate LVIII. figs. 5 & 6) is almost half as long again as is the 
second. It is, like the third of Pelecanus, greatly drawn out, and with the neural spine 
and hypapophysis all but entirely suppressed. There is no interzygapophysial ridge. 
The postaxial half of the median hypapophysial ridge is replaced by a narrow, shallow 
groove, the margins of which must be reckoned as catapophysial, while a parapophysial 
ridge runs along each side of the ventral surface of the centrum, and ends postaxially 
in a rib-like styloid process, which begins to project freely ventrad as well as postaxiad 
at about the preaxial end of the postaxial fourth of the centrum, almost extending 
postaxiad as far as the preaxial end of the postaxial articular surface of the centrum. 
A small tubercle (which may be either the representative of a tubercular process or 
a metapophysis) projects just behind the prazygapophysis and above the tubercle at 
the preaxial end of the parapophysial ridge. From the former tubercle a slight ridge 
descends obliquely to join the parapophysial ridge at about its middle. 
The rourTH verTeprA (Plate LVIII. figs. 7 & 8) is about equal in length to the third, 
and is quite like it, except that the median subcentral groove is a little deeper and 
extends along the whole length of the centrum. At the postaxial end of the preaxial 
third of each lateral margin of the subcentral groove a small catapophysial process 
projects downwards, while between such lateral margin and the more externally situated 
preaxial part of the parapophysial ridge (p') is an antero-posterior groove (fig. 8, 7) which 
corresponds with the similarly situated groove beneath the fifth and sixth vertebre of 
Pelecanus. The styloid process begins to start out at a point slightly more preaxial. 
The rirrH verTesra (Plate LVIII. figs. 9-11) is like the fourth, except that it is 
very slightly shorter, and that the styloid processes are again a little more preaxial, 
and the postzygapophyses extend postaxiad a little beyond their articular surfaces. 
The sixtH verTepra (Plate LVIII. figs. 12-14) is decidedly shorter, not greatly ex- 
ceeding the axis in length; and here, while the catapophysial margins of the sub- 
central groove are more raised, the styloid processes are shorter and more preaxial, 
a wide, subequal, antero-posterior groove extending between the catapophysial and para- 
pophysial ridges. Here a neural spine begins to reappear?, the postzygapophyses are 
1 In Plotus nove-hollandie it begins in the fifth yertebra. 
VOL. X.—PaRT vil. No. 6.— August 1st, 1878. 3c 
