110 



NOETH AMERICAN BIRDS. 



specimens, aided by the important conclusions of Mr. Hancock (Annals and 

 Magazine of Natural History, 2d ser., XIII, 110 ; London, 1834), Schlegel 

 {Falcones, 'M\is6nm d'Histoire Naturelle des Pays-Bas, 1862), Pelzeln (Ueber- 

 sicht der Geier und Falken der Kaiserlichen ornitholofjischen Samniluno-, 

 April, 1863), and Alfred Newton (History of British Birds, revised ed., part 1, 

 June, 1871, pp. 36-52, and Proc. Acad. Nat. Sc. Philadelphia, July, 1871, 

 pp. 94, 95), in their important papers bearing upon this subject, which, though 

 they each express the peculiar individual views of the writer, together clear 

 up pretty satisfactorily the problem of the number, character, and haliitats of 

 the several races, as well as the different phases of variation to which each is 

 subject. 



43139, f 



43139, ^. 



5482, f. 



Fako polyagrus. 



CH- 



Fako sacer. 



In studying the F. lanarius, I have experienced most discouraging dif- 

 ficulties from the want of sufficient series of the Old World races, and from 

 the unsatisfactory character of most descriptions and figures of them, besides 

 being much perplexed by the confusion of their synonymy by different 

 authors. In consequence of this, my diagnoses of the four races of which 

 alone I have seen examples may be very unsatisfactory as regards the 

 characters by which they may be most readily distinguished. Having seen 

 the adult of only a single one of these four races, I am therefore compelled to 

 base my differential characters upon the immature stages. 



In addition to the four races of F. lanarius characterized above, there are 

 several geographical forms belonging to the Old World, chiefly intertropical 

 Asia and Africa. These are the var. hahylonicus, Scl. and Irby, (Gray's Hand 

 List, I, p. 20, No. 173,) of Southeastern Europe and Western Asia ; var. harha- 

 rus, L. (Gray's Hand List, p. 20, No. 174), of Northern Africa ; and var. 

 tanyioterus, Licht. (Gray's Hand List, No. 175), of both the preceding regions, 

 which Mr. Gurney writes me " is simply tlie intertropical race of F. lanarius, 

 from which it only differs in being of a darker shade throughout." The F. 



