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U. S. P. R. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 
olivaceous of the plumage, readily distinguish the specie3 of this genus from any other North 
American flycatchers. The upper plates of the tarsi in a good many species do not encircle the 
outside, but meet there a row on the posterior face. 
There are no species of North American birds more difficult to distinguish than the small 
flycatchers, the characters, though constant, being very slight and almost inappreciable, except 
to a very acute observer. For remarks concerning the genus and its affinities, see page 187 
preceding. 
The following synopsis may aid in distinguishing the species : 
A. Outer tail feather never abruptly margined with white externally. 
Tarsus moderate ; but little longer than the middle toe. Claw of hind toe reaching along 
the middle of the central anterior claw. 
Above rather pure dark olive, not lighter on the rump. Beneath white, 
tinged with sulphur behind, and with olive across the breast. Wing 
bands tinged with yellow olive. Second, third, and fourth quills 
longest ; first between fifth and sixth. Length, 6 inches ; wing, 2.90. 
trailli. 
Tarsus lengthened ; decidedly longer than the middle toe, which is scarcely, if any, 
longer than the hinder one. 
Above dull greenish olive, with a strong tinge of brown, becoming decidedly 
lighter on the rump. Throat whitish ; a gray olive band across the breast ; 
rest of under parts pale yellow. 
Length 5.50 inches ; wing, 2.80 ; tail, 2.50. Third and fourth quills 
longest ; first shorter than sixth. Culmen .35 of an inch ; under 
mandible yellow pusillus. 
Length about 5 inches; wing, 2.65; tail, 2.50. Second and third quills 
longest ; first shorter than fifth. Culmen .30 of an inch long ; under 
mandible brownish minimus. 
Above clear bright olive green, without any brown on the back. 
Beneath white, tinged with greenish yellow on the sides and behind. 
Wing bands tinged with reddish yellow. Second, third, and fourth 
quills much longer than first and fifth. First rather longer than fifth. 
Wing, 3 inches ; tail, 2.75 acadicus. 
Beneath olivaceous yellow, purest behind ; no white on the under surfaces. 
Wing bands greenish white. Length about 5 inches ; wing, 2.80 ; tail, 
2.45. First quill much shorter that fifth .flaviventris. 
Body olive green above and on the breast ; throat gray ; rest of under 
parts sulphur yellow. Wing bands grayish. Length, 5.50 ; wing, 
2.80 ; tail, 2.50. Third quill longest ; first much shorter than fifth. 
Bill very slender hammondii. 
B. Outer tail feather margined abruptly with white externally. Bill very narrow. Tarsi 
unusually long. 
Tail even or rounded. Tarsus as long as the head. Lower mandible 
whitish ; brown at tip. Body above brownish olive. Beneath whitish, 
tinged with yellow behind and with olive on the breast. Wing with 
conspicuous whitish bands. Length, 5.75 inches obscurus. 
