1917.] Chapman, Distribution of Bird-life in Colombia. 383 



This appears to be a very common bird in the humid Tropical Zone of 

 the Pacific coast of Ecuador and Colombia from at least Naranjo, Prov. 

 Guayas, north to Bagado at the head of the Atrato. Further north, both 

 males and females are paler below and less rufescent above than Ecuador 

 specimens, and thus establish the validity of Myrmeciza maculifer cassini 

 (see also remarks under that race). 



While Myrmelastes exsul, of the Canal Zone and northward, is obviously 

 the representative of maculifer, existing material (including a large series 

 from eastern Panama) indicates the non-intergradation of these birds, and 

 this view is supported by the fact that M. m. cassini, the most northern 

 form of maculifer is, in general coloration, further from exsul than is true 

 maculifer of Ecuador. Of the latter form I have twenty specimens (15 males , 

 5 females) from Ecuador. 



Bagado, 1; Baudo, 1; Novita, 6; Juntas de Tamand,, 7; San Jose, 4; 

 Los Cisneros, 6; Barbacoas, 6; Buenavista, Narifio, 1. 



(2091a) Myrmeciza maculifer cassini (Ridgw.). 



Myrmelastes cassini Ridgw., Proe. Biol. Soc. Wash., XXI, 1908, p. 194 (Turbo, 

 Col.). 



Myrmeciza exsul Cass., Proc. Acad. N. S. Phila., 1860, p. 190 (Turbo); Scl. & 

 Salv., p. Z. S. 1879, p. 526 (Neeh6). 



Inhabits the Tropical Zone of the lower Atrato eastward through Antio- 

 quia to the Magdalena and northward to eastern Panama. 



With a large series (sixty-six males, twenty-eight females) before me 

 I find no difficulty in separating birds from western Ecuador and south- 

 western Colombia (Barbacoas) from those from the northern end of the 

 range of this species (Puerto Valdivia and Rio Salaqui, Col., El Real and 

 Tapaliza, eastern Panama). The latter are decidedly paler; the male 

 has the back and flanks more olivaceous less intensely rufescent, the head 

 and undefparts paler gray, the throat less blackish and usually clearly de- 

 marked from the gray breast. The differences in the female are similar 

 in character but are less pronounced. 



Intergradation between these extremes is absolute and intermediate 

 specimens occur in so large a part of the intervening area, that it is wholly 

 impossible to assign definite geographic boundaries to the range of either 

 form. Specimens fairly topotypical of maculifer and others which might 

 with equal truth be referred to cassini are found at the same locality, but, 

 on the whole, the former may be said to be the prevailing form as far north 

 as the upper Atrato, while beyond this cassini occurs. 



Our eastern Panama specimens show no sign of intergradation with M.. 

 exsul exsul of the Canal Zone and westward. 



