Length to end of tail 5 inches, to end of wings 5 1/4, to end of claws 4 1/8; extent of wings 11; bill along the ridge 3/12, along the edge of lower mandible 6 1/2/12; wing from flexure 4 2/12; tail to the fork 1 11/12; to the end 2 4 1/2/12; tarsus 5/12; hind toe 2 1/4/12; its claw 3 1/2/12; middle toe 4 3/4/12, its claw 2 1/2/12.
Adult Female. Plate CCCLXXXV. Fig. 2.
The Female cannot be distinguished from the male by any difference in her external appearance.
Length to end of tail 4 7/8 inches, to end of wings 5 1/4, to end of claws 4.
Young. Plate CCCLXXXV. Fig. 3.
The young when fully fledged, have the bill dusky, with the edges yellow, the feet flesh-coloured, the claws yellowish. The colour of the upper parts is darker, but the feathers are margined with light greyish-brown; the quills brownish-black, the outer very faintly, the inner broadly margined; the tail-feathers greyish-black, edged with greyish-white. The lower parts are white, the throat faintly streaked with dusky; the band across the breast, and the sides, coloured as in the adult, but darker.
On very carefully comparing skins of this Swallow, with a series of those of the Bank Swallow of Europe, procured for me by my esteemed friend, Thomas Durham Weir of Boghead, Esq. an enthusiastic and successful observer of the habits of birds, I can perceive no difference whatever. Old birds compared with old, and young with young, prove perfectly similar. There is, however, another species closely allied to the present, and which might very readily be confounded with it. This species, to which I give the name of Rough-winged Swallow, Hirundo serripennis, I consider it expedient to describe, although it has not as yet been figured by me.
In a male of the present species, from Boston, the palate is flat, the mouth very wide, measuring 5 twelfths across. The tongue is short, triangular, 2 1/2 twelfths long, deeply emarginate and papillate at the base, two of the lateral papillæ much larger than the rest, the tip bluntish and slightly slit. The œsophagus, a b c, is 1 inch 9 twelfths long, narrow, 2 twelfths in diameter, without crop or dilatation. The proventriculus, b, is little enlarged. The stomach, cdef, a gizzard of moderate length, with distinct lateral muscles, and of an elliptical form, is half an inch long, and 5 twelfths broad; its epithelium longitudinally rugous, tough, and light red. It is filled with remains of insects. The intestine, f g h, is 5 1/2 inches long, its greatest diameter 1 1/2 twelfth; the cœca very small, being 1 1/2 twelfth long, and 1/2 twelfth in diameter, their distance from the anus 9 twelfths. There is no essential difference between the digestive organs of this and other swallows, and the Flycatchers, Warblers, and other slender-billed birds.
The trachea is 1 inch 4 twelfths long; slender, flattened, of about 55 unossified rings. The contractor and sterno-tracheal muscles are slender; and there are four pairs of inferior laryngeal muscles