454 



Genus POLYBOEUS, Yibtllot. 



Poli/iorits ViEiLL. Analyse, 1816, 22 [tj-pe Falco IrasiJicnsis Gmel.^P. Ihanis (Mol.)]. 

 Caracara Cuviek, Reg. Auim. 1817 [same type.] 



Osteology. — Skull most like that of PhalGohccnus, but premaxillaries 

 more compressed, dome of the crauium flatter and more horizontal, 

 and the nasal bones and palatines of diflereut form, Nostrils closely 

 approximated in the upper edge of the nasals, oblong and oblique, their 

 upper end being the posterior one. Posterior outline of the palatines 

 nearly truncated, with the postero-lateral outline forming an abrupt 

 angle ; mandible with an acute-oblong vacuity posterior to the middle 

 portion. Length of skull, 3.30-3.35 (1.60-l.Go); breadth, 1.55-1.60; 

 depth, L.20-1.25.* 



Posterior margin af the sternum with a pair of widely-separated, very 

 deep, rounded indentations. Tarsus : tibials. 50 : 4.50. 



PterylosisA — Remiges, 21. Lores, orbital region, cheeks, lower jaw, and 

 chin naked, with very scant fine bristles; the skin brightly colored (red 

 or yellow) in life ; entire cere behind and below the nostril, scantily cov- 

 ered with fine hairs. Entire pileum densely covered with well-developed 

 normal feathers, those of the occiput elongated into a tolerably length- 

 ened, depressed crest; feathers of the nape also well developed. Contour- 

 feathers compact. Eemiges well developed, the primaries nearly twice 

 the secondaries, hard, stiff, the third to fourth longest, the first sliorter 

 than sixth or seventh; inner webs of outer four distinctly, and the fifth 

 just perceptibly, siuuated. Tail about two-thirds the wing, slightly 

 rounded, or nearly even, the webs firm and shafts strong. 



General external features. — General aspect somewhat vulturine, but 

 bearing and manners almost gallinaceous. Isleck and legs very long. 

 Bill very high aud much compressed, the commissure very straight and 

 regular, and nearly parallel with the superior outliue ; cere very narrow, 

 its anterior outline vertical and straight. Nostril very small, linear, 

 obliquely vertical, its upper end being the posterior one; situated in the 

 upper anterior corner of the cere. Feet almost gallinaceous in appear- 



*Tbe mTiuber iu parentheses denotes the length of the premaxillary alone from the 

 point to the beginning of the frontal. 



tNitzsch (]). 63) says that the distribution of the feather-tracts in i\\& Folyhori is 

 much the same as in the JButeoiies. Polyborus is said to dilt'er fTom the other genera of 

 the group "in having the dorsal portioa of the spinal tract elliptically dilated upon 

 the caudal pit, where it incloses a narrow lanceolate insiilar space — a structure which 

 I have never met with elsewhere amc n^x. the Falcons." 



