32 Philippine Journal of Science ia» 



Academy of Natural Sciences of Philadelphia, but was unable 

 to do so. 



It is very much to be regretted that a skull of the harpy eagle 

 is not at hand for comparison with that part of the skeleton of 

 Pithecophaga. Probably there is not a cleaned skull of the harpy 

 eagle in the United States — adult, subadult, or young. This is 

 invariably the case with respect to any bird before a glut takes 

 place in museums and private collections of birds ; the skulls are 

 left in the skins! 



THE CRANIUM, MANDIBLE, AND ASSOCIATED BONES OF PITHECOPHAGA 



It matters but little from what point of view we may regard 

 the cranium of this great eagle, the fact will at once be ap- 

 preciated that at least two of its characters are so pronounced 

 and so characteristic of the species that to confuse this part of 

 the skeleton with the cranium of any other known eagle would 

 be quite out of the question. In the first place, the lacrymal 

 bones and their accessory outer pieces are of great size, while a 

 still more conspicuous character is to be seen in the size and 

 form of the osseous superior mandible ; this is powerfully hooked, 

 with cultrate tomia. It is transversely compressed almost to the 

 last degree, the transverse diameter at the base beneath being 

 slightly less than 2.5 centimeters, while the vertical height at 

 the same point measures nearly 4 centimeters. Measured me- 

 sially below, it has a length of about 5.02 centimeters. Either 

 narial aperture is very large, and these openings do not com- 

 municate through and through ; anteriorly either one merges into 

 the general surface of the side of the beak, while posteriorly 

 greater depth is present, and the surrounding margin is sharp 

 and triangular in outline; the apex of the triangle is posterior 

 and above (Plate I, fig. 1). 



Turning to the large lacrymals mentioned above, their form 

 and proportions are well shown in the illustration (Plate I, fig. 

 2), while the descending limb is portrayed on the same plate. 

 As is the case with so many large raptorial birds, these lacrymal 

 bones, in adult life, do not fuse with the frontal and nasal upon 

 either side nor with the large, subtriangular accessory piece 

 supported at the outer end of each (fig. 2). The descending 

 orbital limb of a lacrymal is constricted superiorly, anteropos- 

 terior^ flattened below, while it is broader and concaved in front 

 from above downward. This part of a lacrymal does not come 

 in contact either with the small, thin pars plana within or 

 with the zygoma below. 



