48 
Philippine Journal of Science 
1919 
base of the radial crest on the palmar aspect of the expanded 
proximal end of this humerus ; it denotes the place of insertion, 
in life, of the pectoralis muscle, and is found in the same location 
in all true eagles. 
All of the ornithic characters seen in the avian humerus, in 
so far as falconine species go, are to be found at the distal end 
of this bone of our present subject, and each and all of them 
are unusually prominent. This applies especially to the two 
articular tubercles, the trachial fossa, and the tendinal grooves 
on the anconal aspect. In the aforesaid fossa a few, small, scat- 
tered, pneumatic foramina may be observed, especially just be- 
yond the radial and ulnar tubercles. 
The radial crest of the left humerus of this individual exhibits 
the results of some previous disease, and it has manifested itself 
in the form of quite an extensive exostosis. The ulnar crest is 
carried down onto the shaft for a distance of about a centimeter 
as a sharp and distinct border; while at its middle we note a 
small foraminal perforation, with a groove leading into or out 
of it, on the palmar surface of the proximal, expanded extremity 
of this bone. 
This foraminal perforation is absent in the radial crest of the 
humerus of the harpy eagle, and the crest itself is of a triangular 
outline (Plate VII, fig. 2) ; while otherwise, in all other matters, 
the two bones are notably similar in these two eagles. How- 
ever, in the harpy it may be noted that the caliber of the shaft 
is greater and presents less sigmoidal curvature. 
In the Korean eagle (Thalia soaetus pelagicus ) the humerus is 
fully 1.5 centimeters longer than it is in Pithecophaga jefferyi; 
it is also straighter and somewhat slenderer. Its large, trian- 
gular, radial crest extends farther down the shaft, while in all 
other respects the two bones are very similar. Curiously enough 
— the above fact notwithstanding — the skull of the Korean bird 
is neither as large nor as massive as is the skull of the eagle of 
the Philippines. This difference is possibly due to a longer wing 
in the former species; but the material is not at hand at this 
writing either to prove or to refute any such statement. 
In September, 1918, I published an account of Pithecophaga 
jefferyi, illustrated by natural-sized figures of its head and foot. 1 
In that article I made the statement that the species was the 
largest of all existing raptorial birds. Possibly this may be so ; 
while, upon the other hand, the big eagle of the Orient ( Thalia - 
1 Am. Forestry 24 (1918) 555-557, 2 figs. 
