Osteology of Palaeoniis. 
583 
the spine for Psittacus eritliacus and Lorlm flavopalUatas that it would be 
quite superfluous to give a detailed description of these bones here for our 
present subject. Taking these bones, vertebra by vertebra, the differences 
are not so very great, though there are, doubtless, specific, as vrell as 
perhaps generic, differences to be found in them. In my own published 
papers on the osteology of the Psittaci, cited above, still further descriptions 
will be found of the vertebrae, as they are found to be in still other forms, 
as the cockatoos, Conurus, and the macaws. 
In Palaeornis the atlas has the articular cup entire, and there is a con- 
spicuous process extending backward from the centrum, On the axis the 
odontoid 'process is extremely minute, while the haemal spine, as is likewise 
the case in the third cervical vertebra, is prominently developed. The 
"carotid canal" is seen to be open, and is only to be observed on the 
sixth, seventh, eighth, and ninth cervicals ; thes3, including the tenth 
cervical, are all without neural spines, while their spine-like pleura pophyses 
are not very long. 
Thirteenth 2i\\di fourteenth cervical vertebrae support will-developed ribs 
of good length, the first being hilf as long as the second, while neither 
bear unciform appendages. 
The five dorsal vertebrae are all separate bones, their neural spines being 
low, and they interlock with each other at their upper anterior and posterior 
angles. Only the fifteenth and sixteenth possess haemal spines, while the 
broad transverse processes on their dorsal aspects develop spine-like meta- 
pophyses that reach across from one vertebra to another. 
The rihs, which are well shown in Plates XL and XLI, are rather delicately 
formed, and all possess epipleural or unciform appendages, those on the last 
pair being small. Each pair articulates with a 2>air of costal ribs reaching 
to the sternum. This is not the case with the costal ribs or haemapophyses 
of the first long, thin pair of pelvic ribs, which latter entirely lack epi- 
pleural processes. Posterior to this pair of ribs there is another pair, 
which last are aborted, short, spiculiform affairs, thoroughly anchylosed to 
the ventral surface of the ilium on either side. 
In Aiimzona leucoce]jhala the dorsal ribs are stouter than in Palaeornis ; 
the last pair bears no unciform processes, and the long, slender haema- 
pophyses of the only pair of pelvic ribs reach the costal border of the 
sternum to articulate on the facets there for them. 
Ara chloroptera has very broad ribs in the dorsal region, and their flat 
and broad epipleural appendages develop in mid-series a descending process 
from the postero-inferior angles. In this macaw the first pair of cervical 
ribs are short, and the elongate second pair have small unciform processes 
upon them. 
Thus it will be observed that important differences exist with respect to 
the cervical and dorsal ribs in the various genera of parrots, and these 
