It has been supposed by some that two different species of Knot occur in the United States, but I am of a different opinion. The dimensions of birds of this family, as well as of many others, are extremely variable; and, on shooting eight or ten Knots, it would be difficult to find two of them having exactly the same size and proportions. If I add to this the very remarkable changes of plumage exhibited by birds of this family before and after maturity, you will not think it strange that WILSON should have mistaken the young of the Knot for a separate species from the old bird in its spring dress. Indeed, I am obliged to tell you that I have been much puzzled, when, on picking up several of these birds from the same flock, I have found some having longer and thicker bills than others, with as strange a difference in the size of their eyes. These differences I have endeavoured to represent in my plate. My friend JOHN BACHMAN states, that this species is quite abundant in South Carolina, in its autumn and spring migrations, but that he has never seen it there in full plumage. In that country it is called the “May Bird,” which, however, is a name also given to the Rice Bird. Along the coasts of our Middle District, it is usually known by the name of “Grey-back.” TRINGA ISLANDICA, CANUTUS, CINEREA, GRISEA, &c. of _Linnæus_ and _Latham, &c._ TRINGA ISLANDICA, _Ch. Bonaparte_, Synopsis of Birds of United States, p. 350. RED-BREASTED SANDPIPER, TRINGA RUFA, _Wils._ Amer. Ornith. vol. vii. p. 43, pl. 57, fig. 5. Summer. ASH-COLOURED SANDPIPER, TRINGA CINEREA, _Wils._ Amer. Ornith. vol. vii. p. 36, pl. 57, fig. 2. Winter. KNOT, or ASH-COLOURED SANDPIPER, _Nuttall_, Manual, vol. ii. p. 125. TRINGA CINEREA, _Richards. and Swains._ Fauna Bor.-Amer. vol. ii. p. 387. Adult Male in Summer. Plate CCCXV. Fig. 1. Bill rather longer than the head, slender, straight, compressed, tapering, with the tip a little enlarged and blunt. Upper mandible with the dorsal line straight, and slightly declinate, the ridge narrow and flattened until towards the end, when it becomes considerably broader, the sides sloping, the tip convex above and ending in a blunt point, the edges thick and flattened. Nasal groove extending to near the tip; nostrils basal, linear, pervious. Lower mandible with the angle long and very narrow, the dorsal line straight, the sides sloping outwards, with a long narrow groove, the tip a little broader, but tapering.