458 Bulletin American Museum of Natural Histori^. [Vol. XXXVI, 



qui, Costa Rica and Nicaragua are not separable from fourteen specimens 

 from western Colombia, while three from the Canal Zone are not separable 

 from an equal number from Bonda, near Santa Marta, Colombia. 



The characters by which accola may be distinguished from pallens are 

 more grayish, less greenish borders to the yellow crown-patch, darker up- 

 perparts, and greater extension posteriorly of the grayish on the breast. 

 The significant character, is, in my opinion, the color of the sides of the 

 crown. In this respect pallens agrees with true viridicata, of which we have 

 five specimens from Paraguay, while accola resembles implacens, of which 

 we have four specimens from western Ecuador. This is in accord with the 

 distribution of the two groups. That is, the green-headed birds from east 

 of the Andes might be expected to occur in the Santa Marta region whence, 

 as in many other species, they have evidently ranged westward to Panama, 

 while the gray-headed birds are West Andean and range from the Pacific 

 coast of Ecuador north to Central America. 



Specimens from the Cauca and Magdalena Valleys are intermediate. 

 The former are nearer accola, the latter, pallens. Myiopagis viridicata im- 

 placens (Scl.) ,of western Ecuador is a somewhat smaller bird than accola 

 with the gray of the head more pronounced and darker. We have taken 

 it in the same localities (vicinity of Guayaquil and Puna Island) as M. svh- 

 placens, a larger bird with a decidedly longer tarsus (tarsus 20-22 mm.), 

 a well-defined superciliary and obscurely streaked throat and breast. 



In some Colombian specimens of accola the tarsus might fairly be called 

 pycnaspidean, the tarsal envelope being incomplete with, in several speci- 

 mens, an indication of tubercles or papillae, on its hinder margin. Others 

 appear to be fairly exaspidean. If my diagnosis of this character is correct 

 its variability in a single species strongly impugns its value in classification. 



Los Cisneros, 3; Caldas, 2; Jiminez, 5; Pavas, 1; Rio Frio, 2. 



Measurements of Males. 



