474 STRUCTURE AND CLASSIFICATION OF BIRDS 



Milvago chimango 

 Gypaetus harhatus 

 Dryotriorchis spectabilis 

 Aquila imperialis 



Melierax polyzonus 

 Polyhorus hrasiliensis 

 Polyboroides typicus 

 Haliaetus alhlcilla 



Lophoaetus occipitalis I Milvus ictinus 



Melierax monogrammicus I Astur approximans 



a wristward branch (as shown in fig. 'A26) is given off, the 

 tendon, in fact, bifurcating. Fuebeingee, however, while 

 figuring the two types, distinguishes in the apparently single 

 tendon of Tinnunculus two separate tendons in close contact 

 for their entire length. 



A further complication is seen in Gypaetus and Gypo- 

 hierax,^ where a small recurrent tendon (patagial fan) joins 

 the anterior branch of the brevis with the longus, a state of 

 affairs found to characterise Serpentarius, as will be pointed 

 out later. 



The expansor secundariorum ^ is present' in Milvago chili' 

 mango, Harpyhaliaetus' coronatus,'Falco, Polyborus, Tinnun- 

 culus, and Microhierax ccerulescen^ ; in others it is absent. 



The anconcBus arises in Polyboroides and in some other 

 types by a single head from the scapula, which is partly 

 fleshy and partly tendinous. In Vultur auricularis, on the 

 other hand, the muscle arises by two completely tendinous 

 heads, so that the muscle has not that value in the classi- 

 fication of the Accipitres that I at one time thought.^ Ihall 



' In Geranomtus vielanoUucus, which has, as have aJl the last-mentioned 

 genera, a bifurcate tendon" of the. brevis, a small muscular belly ending in a 

 tendon which becomes lost upon the patagium ai;ose on the right side, in a, 

 specimen which I dissected, from the extensor muscle near to the end of the 

 anterior branch of the brevis tendon. I am uncertain of the exact homology of 

 this structure in Oeranoaetus. 



' For muscular anatomy, &o,, of Accipitres see Giebel, ' Bemerkungen iiber 

 Catha/ries aura,' &c., Zeitschr. f. d. ges. Naturw. ix. (1857), p. 426 ; ' Zur 

 Anatomic von VtUtur fulvus,' ibid. xxi. (1863), p. 131; 'Zur Anatomie des 

 Lammergeiers,' ibid, xxviii. (1866), p. 149 ; S. Haughton, ' On the Comparative 

 Myology of certain Birds,' P. B. Irish Ac. ix. (1867), p. 524 (crane and goose 

 as well as hawks). He deals with weight only. E. Neandek, UndersSkmnga/r 

 af Mushulaturen hos slagtet Buteo, Lund, 1875 ; Milne-Edwabds in Becherches 

 Anatomiques, Sc, des Oiseaux Fossiles de la France, Paris, 1867. 



' ' On certain Points in the Anatomy of the Accipitres,' P. Z. S. 1889, 

 p. 81. 



