FALCOXID.E — THE FALCOXS. 103 



Family FALCONID^. — The Falcons. 



Char. Eves directed laterally, and eyelids provided with lashes. Toes invariably 

 naked, and tarsus usually naked and scutellate (feathered only in Aquila and Archihuieo). 

 Outer toe not reversible (except in Pandion). Head never with ear-tufts, and never 

 wholly naked (except in the VuUurince, of the Old World). 



The above character.'? are about the only readily observable points in the 

 external anatomy in wliich the Falconidcc differ strikingly from the Striguhc 

 and CatJiiirttda; and may serve to distinguish the birds of this family from 

 those of the two others. The osteological characters, however, as expressed 

 on page 1328, are more decided and important in a taxonomic point of 

 view, and serve to separate the Hawk family as a well-dehned group. 



In the following treatment of the North American Falconidcc, I confine 

 that part relating to the systematic arrangement strictly to the species 

 embraced within the province of our work, for the reason that in a forth- 

 coming monograph of all the American species I hope to present a system- 

 atic classification based upon the species of the whole world. All prelimi- 

 nary details regarding the general characteristics and distinctive peculiarities 

 of the family, as well as all discussions and generalizations upon the subject, 

 will therefore be omitted here. 



The following synopsis of the North American genera is intended as an 

 artificial arrangement which may enable the student to identify, by simple 

 and readily understood characters, the forms belonging to this country.^ 



Genera. 

 A. Nasal bones almost completely ossified, the nostril being a small orifice, with 

 a conspicuous central bony tubercle ; its form nearly or quite circular, or linear 

 and oblique (in Polyborxis), with its upper end the posterior one . . . Falconince. 



1. Falco. Nostril circular. Commissure with a prominent tooth 

 and notch ; lower mandible abruptly truncated and notched. 

 Primaries stiff and hard, and more or less pointed, the first to the 

 second longest, and the outer one or two with their inner webs 

 cut, the angular emargination being near the end of the quill. 

 Middle toe much more than half as long as the tarsus ; claws 

 strongly curved, very acute. 



2. Polyborus. Nostril linear, oblique, the upper end the posterior 

 one ; commissure without prominent tooth nor notch ; lower mandi- 

 ble not distinctly truncated or notched. Primaries soft, obtuse, 

 the third longest, and the outer four or five with their inner webs 

 cut, the shallow sinuation being toward the middle of the quill. 

 Middle toe less than half the tarsus ; claws weakly curved, very 

 obtuse. Face and cheeks naked, and scantily haired. 



1 As in the case of the Sfriyiiki; my determinations of the North American species of Fa/- 

 ctmida: were furnished, according to request, to Dr. Coucs, for use in his " Key to North American 

 Birds." (R. E.) 



