64 BULLETIN 50, UNITED STATES NATIONAL MUSEUM 



<Milvidae Maynard, Birds Eastern North Amer., 1881 (Jan. 26, 1880), 281 

 (includes Circus, Rostrhamus, Elanoides, Iciinia, and Elamis). 



<Haliaetidae Maynard, Birds Eastern North Amer., 1881 (April 16, 1880), 320 

 (for Haliaeetus only). 

 XFalconidae Swann, Monogr. Birds Prey, i, 1925 (includes Polyborinae and 

 Falconinae, leaves out Elaninae and Aegypiinae; also contains Accipitrinae, 

 Buteoninae, Gypaetinae, Aquilinae, Milvinae, and Pandionidae). — Boet- 

 TicHER, Verh. Orn. Ges. Bay., xvii, 1927, 538 (includes Falconinae). 



Nonfalconine Accipitres with coracoids not overlapping at sternum; 

 upper portion of anterior face of tarsometa tarsus without bony ring; 

 outer (fourth) toe not reversible, claws graduated in size, from that of 

 the hallux (largest) to that of outer (fourth) toe (smallest), not con- 

 tracted to their under surface where (except in subfamily Elaninae) 

 broadly grooved or concave (in transverse section) ; deep plantar ten- 

 dons of type III; tendons of biceps not spUt; tensores patagii not pecul- 

 iar; cervical vertebrae 13 or 14; caeca minute; contour feathers with 

 aftershafts. 



Palate indirectly desmognathus or rarely (in Elaninae) schizognath- 

 ous; vomer not expanded anteriorly, not closely applied to the pala- 

 tines; lachrymal usually with an accessory superciliary plate; ant- 

 orbital plate (prefrontal) often much reduced, generally tongue shaped, 

 articulating or even fused by its free end with distal extremity of 

 lachrymal; squamal prominence not strongly developed; ventral sur- 

 face of maxilla without median bony ridge; mandible without ramal 

 vacuity; nasal bones very incompletely ossified, the nostril with a 

 more-or-less oval or pyriform, usually large, external opening, fully 

 exposing the nasal septum, and without any bony (though sometimes 

 with a cartilaginous) central tubercle, or if slitlike the lower end the 

 posterior one, or if small and more or less circular without bony rim 

 or tubercle; procoracoid small, articulating with scapula only and 

 widely separated from clavicle; thoracic vertebrae all free; spina 

 interna sterni absent; syrinx tracheobronchial; no gap between first 

 and second bronchial semirings; eggshells with green translucence. 



The Accipitridae, as here defined, includes all the diurnal Falcones 

 except the Sagittariidae, the Falconidae, and the Pandionidae. It is 

 a very extensive group and constitutes a decidedly heterogeneous 

 assemblage, the modifications of form exhibited by the 70 or more 

 genera (represented by more than 200 species) being so great and 

 various that it is exceedingly difficult to define the group without 

 recourse to anatomical characters. Indeed, probably no existing 

 family of birds presents greater extremes of size or external form; and, 

 in a limited fauna, the gap between the gigantic, filthy vultm-es and 

 comparatively minute members of the genus Accipiter, the heavy, 

 comparatively sluggish hen hawk (Buteo) and the light and graceful 



