BASILEUTERUS.—SETOPHAGA. 177 
In separating this bird from B. delattrii, Mr. Sclater speaks of the greater length of 
its wings!; 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 B. 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 full-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 brunneiceps 1°, 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 José de Costa Rica. 
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 Mniotiltide, it being in this respect quite as well provided with bristles as the 
majority of the Old-World Muscicapide. 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. 
Returning 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 
* This, 1878, p. 302 et seq. 
BIOL. CENTR.-AMER., Aves, Vol. I., October 1881. 23 
