472 STRUCTURE AND CLASSmCATION OF BIRDS 



ACCIPITRES 



Definition. — Aquinoubital. Oil gland present. Two carotids. Skull 

 desmognathous and holorhinal. Cseca rudimentary or absent. 

 Ambiens present. Biceps slip absent. 



This large group of birds admits of but a scanty defini- 

 tion, if we are to include in it, as is here done, the secretary 

 bird and the American vultures ; for it then shows a con- 

 siderable amount of structural variation. The^oil gland, 



Ana 



Fig. 226. — Tensobes Patagh of Polyboroides (after Beddaed). 

 t.p.l, tensor patagii longus ; t.p.hr^ tensor brevis ; Anc^ anconeeus ; By deltoid. 



invariably present, is generally feathered, but nude in the 

 Cathartidse. In Serpentarius this gland varies in size ; in 

 one specimen it was found to be very small and to have a 

 very minute tuft. 



The after shaft is absent in the Cathartidse and in Pandion, 

 present in other Accipitres. Twelve rectrices is the usual 



