(1. Xema, Leach).
Entire length from twelve inches six lines to fourteen inches: length of the bill one inch; of the tarsus one inch six lines; of the tail five inches: breadth, wings extended, about thirty-three inches. Sab.
(Adult male and female in summer). " The whole of the head, and upper part of the neck, a very dark ash or lead-colour; the remainder of the neck behind and before, as well as the breast and belly, pure white; a narrow black collar surrounding the neck at the meeting of the ash-colour and white: back, scapulars, and wing-coverts, ash-coloured, very much lighter than the head, but darker than the corresponding parts of the Larus ridibundus; the lower ends of the scapulars tipped with white: the first five primary quills with black shafts, the whole outer webs of these black, the edge of their upper webs white to within an inch and a half of the tips, the white sometimes continued to the tip; the tips of the first and second of these quills in some white, in others black; the tips of the third, fourth, and fifth, white, giving the wing when closed a spotted appearance; the sixth primary quill with a white shaft, having the web more or less black, but principally white, with sometimes a black spot near the end; the other primaries, the secondaries, and tertials, white; the whole under parts of the wings white: wings extending an inch or more beyond the longest feather of the tail: upper and under tail-coverts white; the tail feathers twelve, the outer narrower than the central ones; the depth of the fork nearly an inch: bill with the base of both mandibles black as far as the angular projection of the lower mandible, the remainder yellow; inside of the mouth bright vermilion: irides dark, surrounded by a naked circle of the same colour as the inside of the mouth; a small white speck beneath the eye, scarcely perceptible: legs black." Sab. In the immature state and in the adult winter plumage, the black head is wanting. (Egg). Of a regular shape, and not much pointed: colour olive, much blotched with brown: long. diam. one inch six lines. Sab.
Two individuals of this species, which was first observed in Greenland by Captain Sabine, are recorded by Mr Thompson* to have been killed in Ireland. The specimens, which are both in the plumage of the first year, are now in the Museums of the Natural History Society of Belfast and the Royal Society of Dublin. Not much is known respecting its habits. Said to lay two eggs on the bare ground, which are hatched in the last week in July. Food, marine insects.
(2. Larus, Steph). * Small; less than twenty inches in length.