BIRDS OF NORTH AND MIDDLE AMERICA 377 



Morphnarchus Ridgway, Smiths. Misc. Coll., Ixxii, No. 4, 1920, 2. (Type, by 



original designation, Leucoptcrnis princeps Sclatcr.) 

 Uruhitinga Reichenow, Die Vogcl, i, 1913, 390, part. 



Rather small to rather large Buteones (wing about 182 to 419 mm.) 

 with middle toe not more than half as long as tarsus, or slightly more 

 than half as long, nostril obliquely oval (vertically oval in L. semi- 

 plumbea) and with coloration black and white, slate color and white, 

 or mostly plain slate color (the tail black and white in varying relative 

 proportion), and with young, where known, not essentially, if at all, 

 different in coloration from adults. 



Bill moderate to rather large in size, similar in form to that of 

 species of Buteo; the culm en (chord) usually less than one- third as 

 long as tarsus; nostril usually obliquely oval or subpyriform (more 

 nearly vertical than horizontal), quite vertical in L. semiplumbca and 

 L. princeps, regularly decurved from base, the maxillary unguis rather 

 long; depth of bill at base of culmen from a little less than, to slightly 

 more than, two-thirds the chord of culmen, its width at same point 

 a little less than three-fifths its depth; gonys slightly convex, ascending 

 terminally, not prominent basally; maxillary tomium slightly convex 

 posterior to postunguinal concavity; length of cere on top a little less 

 than two-thirds the chord of culmen, the upper outline nearly straight 

 but moderately ascending basally, v/here slightly convex, the anterior 

 outline convex in front of nostril but slightly concave and nearly ver- 

 tical below; wing relatively rather short to moderately long, much 

 rounded, the longest primary exceeding distal secondary by about 

 one-fifth (L. semiplumbea) to one-third (L. plumhea) the length of 

 wing; third, third and fourth, or fourth and fifth primaries longest, the 

 first shorter than tenth to equal to ninth; inner webs of four to five 

 outer primaries emarginated or sinuated, usually the four outer emar- 

 ginated, the fifth sinuated. Tail usually between half and two-thirds 

 as long as wing (tw^o-thirds as long in L. semiplumbea and L. plumbea) , 

 its tip usually slightly rounded (truncated in L. semiplumbea and L. 

 schistacea, slightly emarginate in L. princeps). Tarsus less than one- 

 fourth (L. lacernulata) to more than one-third (L. semiplumbea) as 

 long as wing, the upper portion feathered in front and on sides for less 

 than one-third to more than one-third (L. semiplumbea) its length, 

 stout, the acrotarsium and planta tarsi each with a single continuous 

 series of transverse scutella; middle toe less to more than half as long 

 as tarsus (about half as long in L. melanops; more than half as long 

 in L. princeps) ; outer toe decidedly longer than inner toe, extending 

 to or beyond middle of penultimate phalanx of middle toe, the inner 

 extending nearly to middle of same phalanx, except in L. ghiesbreghti , 

 in which it does not extend beyond articulation of second and third 

 phalanges; hallux as long as to much shorter than imier toe, except in 



