This delicately-formed little Swift, conspicuous even in flight, from the broad belt of white across the black body, is a very common species in Jamaica, where it resides all the year. Over the grass-pieces and savannas of the lowlands, the marshy flats at the seaward mouths of the valleys, as well as the pens of the mountain slopes, this swift-winged sylph daily urges its rushing course in parties of half-a-dozen to fifty or a hundred, often mingled with other Swallows, performing mazy evolutions, circling and turning, crossing and recrossing, now darting aloft, now sweeping over the grass, till the eye is wearied with attempting to follow them. The length of its wings, which is scarcely less than that of the whole bird,—renders it a fleet and powerful flier; an attentive observation will be able to identify it, when mingling in aerial career, by a more frequent recurrence of the rapid vibration of the wings, the momentary winnowing, by which a fresh impetus is gained. There is a very interesting structure in the sternum of this bird, which as far as I know is unprecedented. The sternum, though void of emarginations, possesses two oblong foramina of large size, one on each side of the middle of the ridge, and a round one perforating the ridge itself near the front margin. As all three are closed by the usual membrane, the object may be, the decrease of weight by the abstraction of bone, while the surface for the attachment of the muscles of flight remains undiminished. It would be interesting to know whether this structure is found in the Collocaliæ of the Indian Archipelago, to which the present bird bears a strong outward resemblance. The stomach of one, a female, which I dissected, shot while hawking among many others over Bluefields’ grass-piece, in April, was distended almost to bursting with minute insects, which on being dispersed in water, and examined carefully with a lens, proved, I believe exclusively, the winged females of a small species of ant, exceedingly numerous, all more or less comminuted.