24 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



quently obsolete. Wings very long and pointed, reaching when closed 

 to or beyond the end of the tail (or else the latter deeply forked with 

 lateral rectrices much elongated); obvious primaries nine (the tenth 

 very minute and wholly concealed), the longest (ninth or eighth and 

 ninth) more than twice as long as longest secondaries; primaries with 

 edges never sinuated; innermost secondaries ("tertials") never elon- 

 gated. Tail composed of twelve rectrices, more or less emarginated 

 or forked (never rounded nor graduated), never longer than wing (usu- 

 ally much shorter), the lateral pair of rectrices sometimes attenuated 

 and much elongated. Feet small; tarsus never longer than middle toe 

 with claw (usually shorter), more or less distinctly scutellate" (or else, 

 rarely, feathered);* lateral toes about equal, their claws usually reach- 

 ing about to or falling slightly short of base of middle claw, rarely (in 

 genus Olwicola) extending decidedly beyond or falling decidedly 

 short (in genus TachyGmeta); basal phalanx of middle toe adherent to 

 both lateral toes for a portion of its length, more so to the outer toe, 

 which is sometimes united for the whole of the basal phalanx or (more 

 rarely) for a considerable part of the second (subbasal) phalanx; toes 

 with the usual (Passerine) number of phalanges (1, 2, 3, and 4, respec- 

 tively, exclusive of the ungual phalanges). 



Plumage compact, usually lustrous or semimetallic, at least on upper 

 parts, but sometimes dull-colored throughout. The single annual molt 

 takes place, usually at least, in autumn or winter." 



Range. — Cosmopolitan. 



The swallows constitute perhaps the best-defined group among osci- 

 nine birds, and are characterized by their very short, flat, triangular 

 bill, wide gape, extremely long wings, and short tarsi and weak feet 

 (fitted only for perching). They are eminently aerial and insectiv- 

 orous,'* feeditfg on the wing, in all these respects closely resembling 

 the Swifts (Family Micropodidse), from which, however, they differ 

 greatly in structural characters. 



The family is cosmopolitan, though most numerously represented 



«The precise character of scutellation of tarsus is somewhat difficult to make out, 

 owing to a tendency to fusion of the plates, although not essentially different from 

 most Oscines. There is a series of scutqllse along the anterior face of the tarsus, and 

 a longitudinal plate on each side, meeting, but not coalescing, behind. The anterior 

 scutellse sometimes appear to fuse into the outer lateral plate; or sometimes the 

 latter is more or less subdisvided; the inner plate is generally more distinct from the 

 anterior scutellas, and usually entire, except perhaps at the lower extremity. (Baird, 

 Review Am. Birds, pp. 267, 268. ) 



6 In one genus {Chelidonaria Eeichenow) both tarsi and toes are feathered. 



«See Sharpe and Wyatt, Monograph of the Hirundinid», i, xi, and Allen, Auk, 

 xii, 374, 375. 



(^Although mainly insectivorous, the swallows are not entirely so, some species 

 feeding on berries of various sorts when their favorite insect food temporarily fails 

 them owing to sudden or unseasonable changes of weather. 



