AKT. 7 EEVISIOX OF THE GENUS BASILEUTEEUS TODD 9 



group is strictly confined to the Tropical Zone. P. fulvicavda of the 

 upper Amazon, which itself seems allied to a certain section of the 

 genus Basileuteims, may be taken as the primitive form. In central 

 and southeastern Peru (in the Amazonian drainage) it has become 

 slightly modified into a recognizable geographic race, poUothrix. In 

 the valley of the upper Maraiion in northwestern Peru lives stiJi 

 another form, annexa, which diverges toward P. semicervina of 

 v/estern Ecuador and Colombia. The indications are that Phaeoth- 

 lypis^ in common with numerous other avian forms of presumably 

 cis-Andean origin, has crossed the Andes at this point, to extend 

 its range northward on their western side, whence it has passed into 

 the Cauca and Magdalena Valleys. Entering Panama, it has spread 

 northward as far as Honduras, after undergoing further modifica- 

 tion. It is not easy to decide how to rank the various forms from a 

 systematic and nomenclatural standpoint. For the present we are 

 recognizing three species, even while admitting that they probably 

 grade into each other, and that their differential characters are not 

 veiy trenchant. The range of P. semicervina sernicervina is entirely 

 cut off from that of P. fulvicauda by the interposition of the Andean 

 chain, which would tend to justify keeping the two specifically dis- 

 tinct, were it not that the form of the upper Maraiion Valley, as 

 already remarked, appears to be much more closely allied to the 

 former than to the latter, which complicates the situation somewhat. 



K.EiY TO THE SPECIES AND SUBSPECIES OP PHAEOTHLYPIS 



A.' Under parts mottled or clouded with brownish, 

 b.* Under parts more whitish, less buffy. 



Phaeothlypis leucopygia leucopygia. 

 b.'' Under parts more decidedly buffy__Phaeothlypis leucopygia veraguensis, 

 A.^ Under parts without brownish mottling or clouding, 

 b.' Under parts almost uniform buffy. 



c.^ Under parts deeper buffy ; terminal band of tail darker, more 



brownish, less olivaceous Phaeothlypis semicervina semicervina. 



c." Under parts paler buffy ; terminal band of tail lighter, more oliva- 

 ceous, less brownish Phaeothlypis semicervina annexa. 



b.' Under parts whitish, the sides and flanks washed with buffy. 



c* Above more olivaceous, less brownish ; upper tail-coverts and basal 



part of tail paler buffy Phaeothlypis fulvicauda poliothrix. 



c' Above more brownish, less olivaceous ; upper tail-coverts and basal 

 part of tail deeper buffy Phaeothlypis fulvicauda fulvicauda. 



PHAEOTHLYPIS LEUCOPYGIA LEUCOPYGIA (Sclater and Salvln) 



Basileuterus uropygialis (not of Sclater) Lawrence, Ann. Lye. Nat. Hist. 

 N. Y., vol. 8, 1866, p. 179 (Grey town, Nicaragua) ; vol. 9, 1868, p. 95 

 (Angostura and Juiz, Costa Rica). — Salvin, Proc. Zool. Soc. London, 

 1867, p. 136, part ( [Tucurriqui], Costa Rica). — von Fkantzius, Journ. f. 

 Orn., vol. 17, 1869, p. 294 (Costa Rica).— Salvin, Ibis, 1872, p. 313 

 (Chontales, Nicaragua; range). — Boucard, Proc. Zool. Soc. London, 1878, 

 p. 52 (San Carlos, Costa Rica; habits). 



