BASILEUTERUS.— SETOPHAGA. 177 



In separating this bird from B. delattrii, Mr. Sclater speaks of the greater length of 

 its wingsi ; and this feature is also referred to by Prof. Baird^ and by Salvin^ ; but, with 

 a larger series of specimens now before us, we find that the length of the wing varies 

 from 2-04 to 2-4, specimens of JB. delattrii and B. rufifrons having wings measuring 

 between these extremes. The length of the wing, therefore, of B. mesochrysus is 

 not a diagnostic character. The same may be said of the colour of the underparts 

 when fuU-plumaged adult birds are compared. The most trustworthy point of difference 

 is the presence in B. mesochrysus of a grey nape, that part of B. delattrii being olive 

 like the back. 



B. mesochrysus was first described by Mr. Sclater, in 18601, from "Bogota" speci- 

 mens, where the bird would appear to be not uncommon, judging from its frequent 

 occurrence in trade collections from Colombia. Bonaparte, too, seems to have seen it 

 from the same place, though he wrongly identified it with Setophaga hnmndceps i^, so 

 Dr. Cabanis tells us ^. We also know of its presence elsewhere in Colombia, as 

 Mr. Wyatt found it in the Magdalena valley, near Herradura, and Mr. Simons in the 

 Sierra Nevada of Santa Marta, as high as 4000 feet above the sea. 



In Central America it occurs at all elevations, from the low-lying land of the Panama 

 railway up to 4000 feet in the neighbourhood of San Jose de Costa Eica. 



It is, like its allies, an inhabitant of the forests. 



SETOPHAGA. 



Setophaga, Swainson, Zool. Journ. iii. p. 360 (1827). (Type Muscicapa ruticilla, Linn.) 

 Euthlypis, Cabanis, Mus. Hein. i. p. 18. (Type E. lacrymosa.) 



In this genus the rictal bristles are more fully developed than in any other member 

 of the Mniotiltidse, it being in this respect quite as well provided with bristles as the 

 majority of the Old-World Muscicapidse. The presence of a nine- instead of a ten- 

 primaried wing, however, at once shows the true position of Setophaga. Basileuterus 

 is its nearest ally, from which Setophaga differs in having a bill rather wider in propor- 

 tion to its length, in the greater development of the rictal bristles, and in the style of 

 coloration of the tail-feathers. In a recent synopsis of the genus* Salvin recognized 

 fifteen species as belonging to Setophaga, which are mainly distributed over Mexico, 

 Central America, and the Andes of South America, as far as Bolivia. Besides these, 

 one migratory species ranges over most of Eastern North America and the Antilles, one 

 species is found in Venezuela, and another in Guiana. But Setophaga is unrepresented 

 in the valley of the Amazons, South-eastern Brazil, and in all the low-lying forest- 

 country of South America. 



Ketuming to our region, we find Setophaga ruticilla, the single migratory species of 

 the genus, very abundant in the winter season from the sea-level to a height of 7000 or 



* Ibis, 1878, p. 302 et seq. 



BIOL. CENTB.-AMBR., Aves, Vol. I., October 18,81. 23 



