580 Transactions of the Royal Society of South Africa. 
big macaws, as well as the plate-like median partition found in those and 
other representatives of the group, which partition fulfils in part the place 
of a true nasal septum. Possibly this septum may partially be derived 
from either nasal, and this is a point I cannot settle with exactitude without 
seeing the skull of an immature specimen. 
All parrots have the osseous roof of the mouth entire, with its posterior 
boundary a sharp, transverse margin or edge. This area is invariably 
concaved, the outer borders (fonfiia) being sharp. In Palaeornis this edge, 
on either side, presents a distinct notch, as shown in Plate XL, fig. 1. This 
notch is also found in this locality in the skulls of the birds in the genus 
Amazona and many others ; but it is usually absent in macaws — indeed, 
entirely so in Ara chloroptera. On the other hand, in Cacatua the posterior 
two-thirds of the osseous tomial margin of the superior mandible is 
horizontal (parallel to the plane of the superficies of the frontal region of 
the skull), while the anterior third is perpendicular to this, the two edges 
forming a right angle between them. 
Turning to the lateral view, we are to note that Palaeornis forms no excep- 
tion to the general rule for the Psittaci in possessing a nearly straight, long, 
and rather stout quadrato-jugal bar. Posteriorly, it articulates in a little pit 
on a special elevation on the side of the curiously formed quadrate in these 
birds, while anteriorly, it abruptly merges into the infero-posterior angle of 
the upper osseous mandible, in the locality of the maxillo-palatine mass. 
Immediately before doing this, this rod exhibits a very slight disposition to 
enlarge somewhat, evidenced in a compression from above downwards. 
Interest, however, centres on this lateral view of the skull of Palaeornis, as 
in the case of other Psittaci, in the form of the orbit, and the arrangement 
of the bones constituting its limiting periphery. Parrots, almost without 
exception, have the boundary of an orbit wonderfully circular in outline, 
while its margins are, for the most part, thin and sharp. 
As is usually the rule throughout the group, the orbit is entirely 
surrounded by bone. This is effected in Palaeornis docilis by the slender, 
narrow, and transversely compressed, infero-posteriorly extending process of 
the lacrymal bone uniformly curving backwards to touch, but not to fuse 
with, the anterior apex of the squamosal process on the lateral aspect of the 
cranium (Plate XL, fig. 1). This is interesting from the fact that this lower 
boundary of the orbit in this species of parrot is formed almost entirely by 
the backward extension of the lacrymal bone ; that it is the squamosal 
process and not the post-frontal that it seeks in order to complete the ring ; 
and that that process is in no way especially elongated to meet it. 
In the skull of the different species of Ara, in so far as I have examined 
them, the bounding orbital ring is very complete, its lower half being of 
uniform width, with sharp edges above and below, while posteriorly it 
completely fuses with the ^ost frontal i^rocess, and in such a manner, in a skull 
