xv, i Shufeldt: The Monkey-eating Eagle 51 
eal cavity is shallow in the femur in this species, as it is in 
some other eagles. Haliseetus leucocephalus also has a slenderer 
femur, while Thallasoaetus pelagicus has one of moderate pro- 
portions — that is, not as long or as stout as in Pithecophaga, 
and the shaft is slightly more curved. In the femur of this 
species the noteworthy characters consist in the great prominence 
of the tubercle on the outer condyle and the unusual depth of the 
pit on the caput femoris for the ligamentum teres. 
Air does not enter so extensively into the bones of the leg in 
Pithecophaga i as it does in the case of the femur. Still, they are 
to some considerable degree pneumatic ; for, upon ordinary mac- 
eration, the bones largely whiten, though not nearly as much as 
does the femur, while in no part do they turn fatty yellow, as 
happens to the metatarsus and toe bones after similar treatment. 
The tibiotarsus in Pithecophaga measures some 20.4 centi- 
meters in length, and the fibula measures 15.8 centimeters (com- 
pare Plate VII, fig. 1, and Plate IX, figs. 2 and 3). The first- 
named bone is nearly straight from end to end, being but very 
slightly arched to the front. For its distal third it is markedly 
flattened in the anteroposterior direction— less so above, where 
it is flat for its anterior surface and sides, the shaft being here 
trihedral on section. Distally the condyles are very much sup- 
pressed posteriorly and correspondingly pronounced in front, 
where the valley between them is deep. Above them, to the in- 
ner sides, the tendinal groove is of great depth; it is very dis- 
tinctly defined as to its boundaries, and the oblique “tendinal 
bridge” is strong and similarly characterized. 
Proximally the raised ridge for articulation with the fibula 
has a length of 3.5 centimeters and lies wholly within the upper 
third of the shaft, which here is very flat and smooth. Above 
this we note the low and short cnemial processes, separated by 
a wide and rather deep valley. The ectocnemial process termi- 
nates in a rather blunt, down-turned hook, extending but very 
slightly above the summit of the bone. The latter slopes to the 
outer side, and presents a prominent, rounded, articular tubercle 
near the head of the femur, which may or may not be especially 
noticeable in this bone in other eagles. At the sides, as well as 
posteriorly, the summit bulges out over the shaft, being most 
thickened along its inner course, beyond which point a concavity 
occurs, bounded in front by the entocnemial process. 
Turning to the fibula, it is to be observed that its shaft below 
the fibular ridge of the tibiotarsus is long and slender, being 
much compressed anteroposteriorly, opposite the middle third 
