BIRDS OF NORTH AND MIDDLE AMERICA 499 



Spizacircus Kaup, Mus. Senckenb., iii, Heft 3, 1845, 258. (Type, as designated 



by Gray, 1849, Circus macropterus Vieillot = ^guz7a maculosa Vieillot.) 

 Spiziacircus (emendation) Katjp, Arch, fur Naturg., xvi, 1850, 32; in Jardine's 



Contr. Orn., 1850, 58. 

 Spizacinis (lapsus) Giebel, Thesaurus Orn., iii, 1877, 513. 

 Spilocircits Kaup, Isis, 1847, 89, 101. (Type, by monotypy, Circus assiynilis 



Jardine and Selby.) 

 Pterocircus Kaup, Archiv. flir Naturg., xvi, 1850, i, 32. (New name for Glaucop- 



terix Kaup, preoccupied.) 

 Eucircus AcLOQUE, Faune de France, i, 1900, 122. (Type, as designated by 



Richmond, 1917, Falco acruginosus Linnaeus.) 

 Pseudocircus Roberts, Ann. Transv. Mus., viii, 1922, 207. (Type, by original 



designation, Accipiter macrourus Gmelin.) 

 Melanocircus Roberts, Ann. Transv. Mus., viii, 1922, 207. (Type, by original 



designation, Falco maurus Temminck.) 



Very slender, long-winged, long-tailed, slender-legged Buteonidae 

 (wing about 309-457 mm.), with a postauricular transverse line of 

 small, stiff, differently formed feathers (forming a "facial ruff," as in 

 Striges) . 



Bill relatively small, compressed, its depth at base of culmen equal 

 to more than one and a half times (sometimes nearly twice) its width 

 at same point, and equal to about two-thirds the length (chord) 

 of culmen; culmen gradually decurved from base, indistinctly if at 

 all ridged, less than to more than one-fourth as long as tarsus, the 

 maxillary unguis moderately long, very acute to rather obtuse at tip; 

 maxillary tomium very slightly to distinctly sinuated, the convexity 

 posterior to the postunguinal concavity never very conspicuous; 

 gonys about half as long as culmen, nearly straight to moderately 

 convex, ascending terminally; cere relatively long, its length on top 

 equal to at least three-fifths (sometimes three-fourths) the length of 

 culmen, its upper outline strongly ascending posteriorly, its anterior 

 outline strongly sinuate (convex in front of nostril, receding and more 

 or less concave below); nostril relatively large, horizontally oval, 

 ovate, or subpyriform, the smaller end the anterior one. Wing very 

 long and pointed, the longest primary exceeding distal secondary by 

 one-third to nearly three-fifths the length of wing; third, third and 

 fourth, or fourth primary longest, the first usually equal to or longer 

 than sixth, but sometimes shorter than seventh; three to four outer 

 primaries with inner webs emarginated. Tail a little more than half 

 to three-fifths as long as wing, its tip slightly rounded, double-rounded, 

 or slightly doubly emarginate. Tarsus usually about one-fifth as 

 long as wing (less than one-sixth as long in C. pygargus), much less 

 than one-fourth {C. pygargus) to much more than one-third (C. 

 aeruginosus) as long as tail, relatively slender, the upper portion 

 feathered in front for from less than one-third to two-fifths its length, 

 the acrotarsium and planta tarsi each with a single continuous series 



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