On the 12th of November, we took, in Bluefields morass, the nest of a Polytmus, containing two eggs, one of which had the chick considerably advanced, the other was freshly laid. The nest was placed on a hanging twig of a black-mangrove tree, the twig passing perpendicularly through the side, and out at the bottom. It is now before me. It is a very compact cup, 1³⁄₄ inch deep without, and 1 inch deep within; the sides about ¹⁄₄ inch thick, the inner margin a little overarching, so as to narrow the opening: the total diameter at top, 1¹⁄₂ inch; 1 inch in the clear. It is mainly composed of silk-cotton very closely pressed, mixed with the still more glossy cotton of an _asclepias_, particularly around the edge; the seed remaining attached to some of the filaments. On the outside the whole structure is quite covered with spiders’ web, crossed and recrossed in every direction, and made to adhere by some viscous substance, evidently applied after the web was placed, probably saliva. Little bits of pale-green lichen, and fragments of thin laminated bark, are stuck here and there on the outside, by means of the webs having been passed over them. The eggs are long-oval, pure white, save that when fresh, the contents produce a reddish tinge, from the thinness of the shell. Their long diameter ⁷⁄₁₂ inch; short ⁴⁄₁₂. The above may be considered a standard sample of the form, dimensions, and materials of the nest of this species. Variations, however, often occur from local causes. Thus, in the one from Bognie cave, only moss is used, and the base is produced to a lengthened point; one of exceeding beauty now before me, is composed wholly of pure silk-cotton, bound profusely with the finest web, undistinguishable except on close examination; not a fragment of lichen mars the beautiful uniformity of its appearance. Others are studded all over with the lichens, and these, too, have a peculiar rustic prettiness. The situations chosen for nidification, as will have been perceived, are very various.