44 Philippine Journal of Science isi* 



they are highly pneumatic in character, and consequently very 

 light in weight for their size. 



The os furculum, or fourchette, has the form of a very wide- 

 spreading capital U ; the lower part of the arch is not especially 

 strong, while it rapidly increases in size from below upward, 

 to terminate in immense, free clavicular extremities. Either 

 of these is much compressed from side to side, with its great 

 superior end accurately molded, externally, to the mesial head 

 of the scapula of the same side. When duly articulated, its 

 apex barely comes in contact with the anteromesial angle of the 

 head of the scapula of the same side. 



The clavicular limbs of the furculum are greatly compressed 

 from side to side, and the edges thus formed are sharp, espe- 

 cially the mesial ones. There is but small evidence of a hypo- 

 cleidium, and the entire bone is powerfully curved backward 

 and upward. Its pneumatic foramina are principally situated 

 in the concavities of the upper clavicular extremities, upon their 

 moderately shallow outer concavities, on that part of the bone, 

 upon either side, which goes to complete the foraminal passage 

 among the heads of the three bones of this girdle. 



The os furculum in the skeleton of our subj.ect agrees very 

 well with the corresponding bone in the harpy eagle ; though in 

 the latter species the free clavicular ends are more extensively 

 rounded off than they are in the case of the Philippine bird. 

 Our white-headed eagle possesses a more delicately fashioned 

 furculum, while in such a form as Thallasoaetus pelagicus, of 

 Korea, the clavicular free ends are enormously developed; but, 

 owing to the high degree of pneumaticity, the bone, as a whole, 

 is extremely light in weight. Doubtless other eagles present 

 still other differences, not only in the furculum, but also in the 

 remaining bones of the girdle. 



When articulated as in life, the coracoids in Pithecophaga do 

 not meet in the median line, being separated by an interval of 

 several millimeters. Either bone is very massive in form ; but 

 is light in weight, owing to the high degree of pneumaticity it 

 enjoys. All of its parts are conspicuously developed, the broad 

 scapular process being perforated by a foramen piercing it from 

 before backward. There may be pneumatic foramina of some 

 size on the mesial aspect of the big head of the bone and still 

 others on its outer aspect. A sternal extremity is considerably 

 expanded, the bone in articulation extending beyond the sternum 

 laterally. Here it is much compressed from before backward, 

 and thickened at its mesial an<?le. 



