8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I45 



Females (lo specimens), wing 62.7-67.0 (64.2), tail 40.2-47.6 

 (43.3), culmen from base 19.9-22.2 (20.8), tarsus 26.4-29.6 (28.1) 

 mm. 



Type, male, wing 66.8, tail 42.5, culmen from base 20.7, tarsus 

 28.2 mm. 



Range. — Eastern Panama; on the Pacific slope from the western 

 end of the Cerro Azul east through the Province of Panama to 

 western Darien ; on the Caribbean slope from the upper Chagres 

 Valley, above Madden Lake (Quebrada Candelaria on the Rio 

 Pequeni, Quebrada Peluca on the Rio Boqueron), and western 

 Comarca de San Bias (Mandinga) east to the Colombian boundary, 

 and beyond to Acandi in northernmost Choco, Colombia. 



Remarks. — The wing coverts are plain in most individuals of this 

 race, with the white spotting typical of M. e. cassini and M. e. 

 macuHfer found only casually in a few. Specimens from the middle 

 Chucunaque Valley, near the mouth of the Rio Tuquesa, are inter- 

 mediate between the new form and cassiui, which ranges through 

 the rest of the lowlands of the Tuira basin. 



The name niglanis is taken from the Greek viyAa/aos, a small fife, 

 in allusion to the whistled calls of these birds, heard constantly as 

 they move through the undergrowth on the forest floor. 



IV. THE GEOGRAPHIC RACES OF THE SILVER-THROATED 

 TANAGER, TANGARA ICTEROCEPHALA (BONAPARTE) 



Specimens now available, particularly those from Costa Rica and the 

 western half of Panama, permit a better understanding of geographic 

 variation in the tanager Tangara icteroccphala (Bonaparte). The 

 species, described from Ecuador in 185 1, soon was recorded also from 

 Costa Rica, and from Veraguas and Chiriqui in western Panama. 

 Cabanis, in 1861, named the Costa Rican bird frantsU, but Ridgway 

 in 1902, with limited series, was not able to distinguish this as a 

 separate race. Hellmayr, in 1936, and others have followed Ridgway 's 

 treatment, though with indication by some that there may be two 

 forms. It is only recently that De Schauensee, in 1951, in his account 

 of the birds of Colombia, recognized formally that there are two 

 races. The uncertainty has resulted from the interesting fact that 

 the populations of these birds in Ecuador and in Costa Rica both 

 are bright in color, which obscures their differences. Specimens that 

 I have collected in recent years from the mountains immediately west 

 of the Canal Zone include another subspecies distinct from both of 

 the others. 



Females in all three races are duller, more greenish throughout, a 



