minence or angle being formed at their junction, as in Gulls, the sides erect
and slightly convex, the edges sharp and' inclinate, the tip acuminate, the
gap-line slightly arcuate.
Head of moderate size, ovate; neck of moderate length; body slender. Feet small; tibia bare for seven-twelfths of an inch; tarsus very short, compressed, anteriorly scutellate; toes small, slender; the first extremely small, the third longest, the fourth much longer than the second; all scutel- late above, the anterior connected by" reticulate webs, of which the inner is more deeply emarginate. Claws moderately arched, compressed, very slender, that of the middle toe much larger, and having its inner edge somewhat dilated.
Plumage soft, close, blended, very short on the fore part of the head. Wings very long, narrow, and pointed; primary quills tapering to an obtuse point; the first longest, the second half an inch shorter, the rest rapidly graduated; secondaries short, incurved, obliquely pointed, some of the inner proportionally longer and narrower. Tail of moderate length, deeply forked, of twelve feathers, of which the middle are rounded, and three inches and a quarter shorter than the outer, which taper to a slender point. Bill black, with the base of the lower mandible tinged with brown, and a very small portion of the tip yellowish. Iris brown. Feet orange-yellow; claws dusky. Surrounding the eye, and extending toward the nape, is a broad band of black; the fore part of the head, the lower eyelid, and all the under parts are pure white; the hind part of the head and the nape are dusky- grey, mixed with white. The rest of the upper parts are light greyish-blue, excepting the rump, which is white, the primary coverts and quills as well as the tail-feathers and their coverts are hoary, with the shafts white; but five of the quills are dusky on the outer web, on the inner along the shaft, and on the inner margin toward the end.
Length to end of tail 15^ inches; bill along the ridge I-/2, along the edge of lower mandible 2-^'i wing from flexure lOy^; tail to end of middle feather 2^, to end of longest feather 6j2; tarsus y§; hind toe T 3 2, its claw y 2 2-; middle toe T §, its claw -ff.
This species differs from the Marsh Tern, Sterna anglica, in being less robust, in having the bill a little longer and much more slender, its height at the angle being f -f, whereas in that species it is yf ; in having the tarsus shorter and much more slender, the feet yellow instead of being black, the claws more slender, and the tail more deeply forked.
The figure in the plate, which is that of an adult bird yet in its winter plumage, has the lateral tail-feathers obliquely truncate, but this was caused by accident, for these feathers in my other specimens run to a narrow point. My specimens from Texas are also in their winter plumage. One of them
