Osteology of Palaeoruis. 
589 
smooth summit of the shaft, while there is no evidence of a trochanter minor 
being present. Distally, the condyles are small, with a very shallow 
popliteal excavation between them posteriorly, and a not much deeper 
channel, or rotular channel, as Sir Richard Owen called it, between them 
on the anterior aspect. As usual, the external condyle is grooved to receive 
the head of the fibula when the leg bones are duly articulated. 
All parrots and macaws possess a imtella of fair size ; and, in so far as 
I have examined it, I may say that it seems invariably to possess a flat area 
proximally, with a continuous sharp edge for the sides and below, and an 
elevated surface posteriorly, the anterior surface being moderately convex. 
Occasionally we may find exceptions to this ; for in Amazona leucocephala 
the patella is very small, and its superior surface exhibits more of a 
concavity. This species has a femur which, while somewhat larger, never- 
theless closely resembles that bone in Palaeornis. 
In our subject, the tibio-tarsus is as straight as its femur, and its shaft 
is, comparatively speaking, equally slender. 
The cnemial i^TOcesses are both greatly reduced, and proximally they may 
be said to be about on the level with the summit of the shaft. 
Distally, the condyles are but moderately developed, and, as in all 
parrots and macaws, the outer condyle is notably smaller than the inner one. 
At the lower third of the bone in front, the tendinal groove is short and 
shallow, and as in Psittaci generally, it is twice spanned by tendinous 
bridges to hold the tendons in the aforesaid groove, the upper one being 
obliquely attached, with its outer extremity the lower. In Amazona oratrix 
the tibio-tarsus is considerably compressed from before backwards, giving 
it the appearance of some fossil specimens of this bone. 
The "fibular ridge" occupies its usual site, the fibula itself being a 
feebly developed bone, and when articulated extends only a short distance 
below this ridge as a fine, hair-like prolongation. Macaws, in which the 
fibula is comparatively much stouter, have the bone even shorter than in 
Palaeornis, for it does not extend below the fibular ridge at all. This is 
likewise the case in Amazona oratrix, and in probably other Psittaci, 
while in the entire assemblage it is a short bone, though one sometimes 
well developed for what there is of it. 
Coming to the tar so -metatarsus there is first to be noted its extreme 
shortness when compared with the other bones of the thigh and leg. For 
example, in Palaeornis docilis, where the femur has a length of 3*1 cms., 
the tibio-tarsus 4-3 cms., the tarso-metatarsus possesses a length of but 
1'6 cms. Other Psittaci exhibit similar proportions upon measuring these 
several bones. Its distal extremity in Palaeornis docilis, and in other 
parrots, cockatoos, and macaws is much compressed from before backwards, 
and much spread out transversely. This is due to the conformation of the 
trochlear prolongations, wdiich are fashioned to adapt themselves to the 
