90 PROCEEDINGS OF THE ACADEMY OF 



and C. pennsylvanicus (Wils.), except in the southern portion ; 

 but Middle and South America have in addition to these (which 

 are there winter migrants from the north), C. albicaudatus (Vieill.), 

 G. erylhronotus (King), G. poliosomus (Quoy and Gaim.), and G. 

 galapagoensis, Gould. 



Among the species composing the subgenus Graxirex there is 

 considerable variation in proportions and size, though nothing of 

 greater than specific importance, since no two are exactly alike in 

 the details of form. G. swainsoni and C. albicaudatus have very 

 long wings, reaching nearly to the end of the tail ; but the latter has 

 a conspicuously longer and thicker tarsus than the former; G. 

 erythronotus agrees wonderfully with C. albicaudatus in its colors 

 and changes of plumage, but in form it is intermediate between 

 that species and G. poliosomus. On the other hand, there is quite 

 a contrast between the great G. galapagoensis and the little C. 

 pennsylvanicus : still, in the subgeneric character of only three 

 primaries emarginated, even tail, etc., they all strictly agree. 

 Several names have been invented to designate these variations 

 of form, but they are not admissible. The synonymy of the sub- 

 genus stands as follows: 



Graxirex, Gould, Darwin's Voyage of the Beagle, Birds, 1841, 22 (type, 



Polyborus galapagoensis, Gould). 

 Tacliytriorchis, Kaup, Classif. Saiig. Vog., 1844, 143 (type, Falco pteroeles, 



Teuim., =Buteo albicaudatus, Vieill.). 

 Pacilopternis, Kaup, Isis, 1847, 329 (type, Falco pennsylvanicus, Wilson). 



Authors have been exceedingly inconsistent in regard to the 

 classification of the American Buteones. Thus, one of our latest 

 and best authorities, Mr. Sharpe, 1 places G. albicaudatus and 

 Buteo abbreviatus together in the so-called genus " Tachytriorchis" 

 (=Craxirex, Syn.), composed, according to his arrangement, 

 solel} r of these two species. The latter of these, however, belongs 

 to the group having four primaries emarginated, and is, conse- 

 quent^, and for other reasons, a true Buteo. The incongruity of 

 arrangement is still further increased by the placing of C. gala- 

 pagoensis, G. poliosomus, G. erythronotiis, C. albicaudatus, G. 

 swainsoni, and C. pennsylvanicus in the genus Buteo (as sepa- 

 rated from " Tachy trior chis"), and scattered among species of no 



1 Catalogue of the Accipitres, or Diurnal Birds of Prey, in the collec- 

 tion of the British Museum. By R. Bowdler Sharpe, London, 1874. 



