_Accipiter_, BRISS. 1760. (Type, _Falco nisus_, LINN.) _Nisus_, CUV. 1799. (Same type.) _Astur_, LACÉP. 1801. (Type, _Falco palumbarius_, LINN.) _Dædalion_, SAVIG. 1809. (Same type.) _Dædalium_, AGASS. (Same type.) _Sparvius_, VIEILL. 1816. (Same type.) _Jerax_, LEACH, 1816. (Same type.) _Aster_, SWAINS. 1837. (Same type.) _Micronisus_, GRAY, 1840. (Type, _Falco gabar_, DAUD.) _Phabotypus_, GLOG. 1842. (Same type.) _Hieraspiza_, 1844, _Jeraspiza_, 1851, and _Teraspiza_, 1867, KAUP. (Type, _Falco tinus_, LATHAM.) _Hieracospiza_, AGAS. (Same type.) _Nisastur_, BLAS. 1844. (Same type.) _Urospiza_, 1845, _Urospizia_, 1848, and _Uraspiza_, 1867, KAUP. (Type, _Sparvius cirrhocephalus_, VIEILL.) _Leucospiza_, KAUP, 1851. (Type, _Falco novæ-hollandiæ_, GMEL.) _Cooperastur_, BONAP. 1854. (Type, _Accipiter cooperi_, BONAP.) _Erythrospiza_, KAUP, 1867. (Type, _A. trinotatus_ TEMM.? not of BONAP. 1830!) GEN. CHAR. Form slender, the tail long, the wings short and rounded, the feet slender, the head small, and bill rather weak. Bill nearly as high through the base as the length of the chord of the culmen, its upper outline greatly ascending basally; commissure with a prominent festoon. Superciliary shield very prominent. Nostril broadly ovate, obliquely horizontal. Tarsus longer than the middle toe, the frontal and posterior series of regular transverse scutellæ very distinct, and continuous, sometimes fused into a continuous plate (as in the _Turdinæ_!). Outer toe longer than the inner; claws strongly curved, very acute. Wing short, much rounded, very concave beneath; third to fifth quills longest; first usually shortest, never longer than the sixth; outer three to five with inner webs cut (usually sinuated). Tail long, nearly equal to wing, usually rounded, sometimes even, more rarely graduated (_Astur macrourus_) or emarginated (some species of subgenus _Nisus_). Subgenera. Less than one third of the upper portion of the tarsus feathered in front, the feathering widely separated behind; frontal transverse scutellæ of the tarsus and toes uninterrupted in the neighborhood of the digito-tarsal joint, but continuous from knees to claws. Tarsal scutellæ sometimes fused into a continuous plate … _Nisus._ More than one third (about one half) of the upper portion of the tarsus feathered in front, the feathering scarcely separated behind; frontal transverse scutellæ of the tarsus and toes interrupted in the region of the digito-tarsal joint, where replaced by irregular small scales. Tarsal scutellæ never fused … _Astur._