Family I. Columbadæ.
(Pigeons.)
The Pigeons have the beak of moderate length, somewhat slender, swollen towards the tip, which is curved downwards: the base of the upper mandible is covered with a soft skin, inflated on each side, in which the nostrils are pierced. The wings vary in length, and in adaptation to powerful flight. The feet are comparatively short; the toes, divided to the base, are arranged three in front, and one behind; they have no spurs.
HEAD OF PIGEON.
"One part of the internal organization of the Pigeon is worthy of special notice. The crop, in the state which is adapted for ordinary digestion, is thin and membranous, and the internal surface is smooth; but by the time the young are about to be hatched, the whole, except that part which lies on the trachea [or wind-pipe] becomes thicker, and puts on a glandular appearance, having its
