ILLUSTRATIONS 
[All the figures are reproductions of photographs by the author made direct from the 
specimens.] 
Plate I 
Fig. 1. Pithecophaga jefferyi, adult; right lateral view of the skull, 
natural size. All the bones of this bird figured on the plates 
are of two individuals. The specimens were received from 
Mr. R. C. McGregor, of the Bureau of Science, Manila, P. I. 
2. The skull shown in fig. 1, seen directly from above, natural size. 
Plate II 
Fig. 1. Halissetus leucocephalus, white-headed eagle, sex?, adult; cranium, 
direct view from above, very slightly reduced. Median lon- 
gitudinal diameter measures 11.1 centimeters in this specimen. 
No. 19278, United States National Museum collection. This 
skull belongs to the skeleton of the specimen used throughout 
this paper. 
2. Aquila chrysaetos, female, adult; cranium, direct view from above, 
very slightly reduced. Median longitudinal diameter measures 
11.9 centimeters in this specimen. No. 18802, United States 
National Museum collection. 
3. Morphnus guianensis, sex?, adult; cranium, direct view from above, 
very slightly reduced. Median longitudinal diameter measures 
9 centimeters in this specimen. No. 18468, United States 
National Museum collection. 
Plate III 
[All figures of Plate III natural size and from the same species, Pithecophaga jefferyi.] 
Fig. 1. The six caudal vertebras (a to b) arranged in normal sequence 
and viewed from above; a, anterior one of chain. 
2. Pygoktyle, right lateral aspect. Lower part pierced by a foramen. 
3. Fifth cervical vertebra, seen from above. 
4. Mandible, seen from above. 
5. Anterior aspect of ninth cervical vertebra. 
6. Trachea, twisted and distorted through drying; fragments of 
bronchial tubes at inner end. 
7. The atlas, posterior aspect. 
8. Anterior view of axis; neural spine directed downward. 
9. Sclerotal circlets of the eyes; elements as they occur or are 
arranged in life. 
10. Hyoid arches viewed from above, with larynx in situ; the latter 
removed at a point seen at the outer end of the trachea in fig. 6. 
Plate IV 
Pithecophaga jefferyi; right lateral view of the trunk skeleton, including 
bones of the shoulder girdle, reduced about one-third. The 
pygostylp and the six caudal vertebras preceding it have been 
removed. 
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