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OUTLINES OF A NATURAL ARRANGM,ENTa|jH'EJrafcGpm^. 



By Eobert Ridgway. 



[Read before the Philosophical Society of Washington, April, 1875.] 



Until very recently, life Birds of Prey have been classified entirely 

 according to their external characters„the primary division being into 

 three so-called families; as ' follows : (1) Vulturidw, or vultures, char- 

 acterized by their naked heads, sluggish habits, and filthy food; (2) 

 Falconidce, or falcons, hawks, eagles, and other diurnal birds of prey, 

 distinguished by their feathered head and predatory nature ; and (3) 

 Strigidw, or owls, known from both the preceding -by having the eyes 

 directed forward, instead of laterally, and by being nocturnal. 



lifotwithstanding the fact that occasional genera constituted transi- 

 tional forms intermediate between two "families",* the above classifi- 

 cation was adopted almost universally until the year 1867, when Pro- 

 fessor Huxley clearly demonstratedt .thaLtiie so-called family Ykdturidce 

 had no existence in fact, it beingiian'iihnajfliral associa*i6fi.vof.haembers 

 of two very distinct families, viz, the Catfiartidce, or American vultures, 

 on the one hand, and a group of the Falconidce (the Old- World vultures) 

 on the other. Besides the announcement of the above important dis- 

 covery. Professor Huxley also proved that the secretary bird (Serpenta- 

 rius reptilivorus), previously included among the Falconidce, was in real- 

 ity the sole Tepresentative of a very distinct family, which he named 

 " Oypogeranidce.^' 



To sum up the important results of Professor Huxley's studies of the 

 osteology of the raptorial birds, they are briefly as follows : (1) The de- 

 molition of the old so-called family Vulturidce, the typical members of 

 which were referred to the Falconidce ; (2) the recognition of a separate 

 family, GathartidcB, to accommodate the aberrant ones ; and (3) the re- 

 moval of Serpentarius from the Falconidce and its establishment as a 

 distinct family, "6yp6geramdcB.'" The families of diurnal Eaptores, ac- 

 cording to Huxley's views, then were as follows : (1) Gathartidw (Amer- 

 ican vultures) ; (2) Gypaetidee (=Falconidce, hawks, «&c., including the 

 Old-World vultures) ; and (3) Gypogeranidce {=Serpentariidce, the secre- 

 tary bird). 



After a very cateful consideration of all that relates to the principles 

 of a natural classification, I find every reason -for adopting, without 

 hesitation, Mr. Huxley's conclusions. | 



* Examples of these perplexing "intermediate" forms are the genera Gypaetus and Poly- 

 borus, among the Falconida, which combine " vulturine " and "falconine" characteristics 

 of habits and external appearance ; while among the Strigidm the genus Surnia is strictly 

 diurnal, and its appearance decidedly hawk-like. The falconine genus Circus, on the other 

 hand, has a distinct facial ruff and other characteristics belonging chiefly to the owls. 

 These cases were very embarrassing to the followers of the old classification, and by different 

 authors were shifted from one family to the other. 



+ Proceedings of the Zoological Society of London, 1867, pp. 440, 443, 462, 465. 



+ I cannot follow, however, in substituting the name GypaetidcE for the old term Falconida, 

 which in its former signification is sufficiently comprehensive to justify its continued use 

 as the proper name for this family ; the term Gypogeranida is equally objectionable, since 

 Gypogeranus (lUiger, 1811) is antedated hy Serpentarius (Cuvier, 1798), in consequence 

 of which Serpentariidce (Selys, 1842), as adopted by Gray (Hand List, 1869, p. 38), is 

 preferable. 



