xv, i Shufeldt: The Monkey -eating Eagle 47 
of the xiphoidal foramina, and that border presents a squarish 
prolongation of no great size in the middle line; it possesses all 
the other aquiline characters of this bone. 
In the bearded vulture, of Europe, the body of the sternum 
is square in outline, and not a parallelogram as in eagles; its 
coracoidal grooves do not decussate, and it has but six pairs of 
costal ribs. In fact, the bone is that of a big vulture, and in 
no way suggests that of an aquiline species of any sort. 
The pectoral limb . — Plates VII and VIII. It has long been a 
well-known fact that all big raptorial birds possess limbs of great 
size, power, and proportions. ' This is what we would usually 
look for when we come to consider their habits and the character 
of their prey. It also explains the fact that most of the bones 
of their limbs enjoy a very perfect state of pneumaticity ; the 
skeleton of the foot, however, often forms an exception to this 
condition. Possibly, in some of our eagles, even the foot bones 
may be pneumatic; they appear to be so in some degree in our 
white-headed species, but surely not in the golden eagle. True 
vultures, almost without exception, possess a skeleton presenting 
a lightness and an extremely perfect pneumaticity unequaled 
by any other family of birds. Gypaetus forms a partial excep- 
tion to this rule, in so far as the skeleton of its feet is concerned ; 
but this bearded species approaches the eagles, while our Amer- 
ican vultures are birds that practice long-sustained and steady 
flight, and do not capture their prey — hence a more perfect aera- 
tion has evolved in them. 
In the different species of eagles, in so far as I have examined 
them, the humerus varies but little in form or in general char- 
acters. It is invariably a large and thoroughly pneumatic bone, 
and to this statement Pithecophaga presents no exception. It 
has a length of about 20 centimeters; and, taken as a whole, its 
shaft presents the “sigmoid curve” in a nearly perfect degree. 
Rather less than its middle third is very smooth and quite cy- 
lindrical in form. Its radial crest is short and triangular in 
outline, while the ulnar tuberosity is very conspicuously de- 
veloped and arches over — to some considerable extent prox- 
imally — the deep pneumatic fossa, in which may be seen the 
pneumatic foramina of very large size, but generally few in 
number. There is also a row of these foramina along the base 
of the smooth, elliptical head of the bone on the anconal side; 
they are of no great size in this locality. A very distinct elon- 
gate elliptical area — raised above the general surface — with its 
major axis parallel to the bone’s shaft, may be seen at the distal 
