Osteology of Palaeornis. 
585 
chloroptera — the Eed and Blue Macaw — is entirely at variance with this 
again, for it has Jive very large caudal vertebrae, and, for a parrot, an 
unusually large pygostyle, which is drawn out superiorly into a point, while 
it exhibits the thickened hinder border, the foramen, and the pit found in 
the pygostyle of Palaeornis docilis as described above. In this macaw, too, 
the last two uro-sacral vertehrae, thoroughly anchylosed with the others, are 
found beyond tlie iliac bones of the pelvis. In this big parrot also we find 
the ilio-ischiadic notches on the posterior pelvic borders to be quite promi- 
nently defined, which, as I have said, is not usually the case in this bone 
among the Psittaci. 
Passing to the bones of the shoulder -girdle we are to note that, although 
the OS furcula is completely developed, it is nevertheless by no means a 
strong bone. It has the U pattern in outline and lacks a hypocleidium, 
while it is greatly compressed throughout its extent. This compression is 
in the antero-posterior direction below, and transversely for the clavicular 
limbs above, including the superior heads of the bone, each one of which 
latter exhibits considerable expansion whereby a thin, fiat surface is pro- 
duced — a surface which, when the os furcula is duly articulated, is pressed 
snugly against the coracoid of the same side, touching the scapula 
posteriorly, thus ensuring the formation of a completed ^oraij/m triosseum. 
Cockatoos, macaws, and representatives of the genus Amazona. and 
numerous others, possess a clavicular arch more or less like what is found 
in Palaeornis, while, in some other parrots, the bone is more or less 
imperfect below or else very rudimentary, as in Calyptorhynchus ; in Ara 
chlorojjtera the os furculum is, while much flattened, strong and complete. 
Palaeornis possesses a neat pair of scapulae, each bone being rather short 
and small when compared with the size of the bird. One of these scapulae 
closely resembles in form the blade of a scimitar, being thin, sharply 
pointed posteriorly, curved, and lacking in any angle on its mesial edge, 
where it is seen to occur in the scapula of many other species of birds. 
Its head forms about one-third of the articular surface of the glenoid cavity 
for the head of the humerus. 
The coracoids, when articulated as in life, are in contact with each other 
in the coracoidal grooves of the sternum. In Am the contact is quite 
extensive. At its sternal extremity the coracoid of Palaeornis is consider- 
ably expanded, and there is developed at its infero- external angle, or rather 
just above it, the process — here quite conspicuous — which is found in the 
same locality in representatives of other groups of birds widely I'emoved 
from the Psittaci. The coracoidal shaft is straight, stout, and smooth, 
while the enlarged upper end of the bone is peculiarly excavated on its 
mesial aspect just below the summit. In Ara cliloroptera this excavation 
is very extensive, forming a striking feature of the bulky head of the cora- 
coid of that bird. At its base occur numerous pneumatic foramina. I may 
