its length from the tip of the lower mandible is twenty-one and a half inches. It is formed of the skin, which is thin, transparent, elastic, rugous, highly vascular, and capable of being expanded like a net, supported by the elastic mandibles to the breadth of nine and a half inches. Head small, oblong; neck long, stout; body full, rather flattened. Feet short and very stout; tibia bare at its lower part, covered all round with small scales; tarsus short, very stout, compressed, covered all round with hexagonal scales, of which the anterior are much larger; toes in the same plane, all connected by reticulated webs, the first shortest, the second an inch shorter than the fourth, which is considerably longer than the third, scaly at the base, scutellate over the rest of their extent. Claws short, strong, curved, rather blunt, that of the middle toe with a sharp pectinate inner edge. Feathers of the head and neck exceedingly small, slender, and of a downy texture, those on the fore part of the head a little more compact; on the nape they are elongated, acuminate, and form a longitudinal narrow crest, which runs down the back of the neck. The feathers in general are lanceolate, acuminate, and of moderately dense texture; those at the junction of the neck and breast anteriorly are stiffer and more elongated. Wings very long, rather narrow, rounded; the humerus and cubitus very long in proportion; primaries much curved; secondaries rather narrow, also incurved toward the end, the inner extending when the wing is closed far beyond the tips of the primaries. Tail short, broad, rounded, of _twenty-four_ feathers, which are broad and abruptly acuminate. Bill bare, space about the eye, and feet, rich bright yellow, becoming brighter before their departure for their breeding grounds; claws yellowish-brown; tip of the bill brighter than the rest. Iris white, in younger birds dusky. The general colour of the plumage is pure white; the crest, the elongated feathers on the fore part of the breast, and those near the edge of the cubitus, pale yellow. The alula, primary coverts, and primary quills, black, the shafts white, becoming brownish-black, toward the end. The inner ten secondaries are white, the rest black, more or less tipped with greyish-white, their bases white, that colour more extended on the inner than the outer, the shafts of all the quills white beneath, those of the secondaries tinged with grey. Dimensions of an old male. Length to end of tail 61-3/4 inches, to end of wing 61-3/4, to end of claws 66-3/4, from the point of the bill to the carpal joint 40; extent of wings 103; wing from flexure 24-1/2; length of cubitus 15; tail 6-1/4; bill along the ridge 13-3/4, along the edge of lower mandible 15; breadth of lower mandible at the base 2; bare part of tibia 1; tarsus 4-8/12; middle toe 4-1/2, its claw 5/8; outer toe 4-1/2, its claw 6/12; inner toe 3, its claw 7/12; hind toe 1-3/4, its claw 8/12. Weight 17-1/2 lb.