The nest is a very wonderful structure, and is usually attached to three upright stems; it is domed, oval-shaped, about nine inches deep, and the small circular aperture which is close to the top is protected by a sloping tile-like projection. It is built of tough grass-leaves, which are apparently first daubed with wet clay and then ingeniously woven in, with the addition, I think, of some kind of mucilage: the whole nest is, when finished, light but very strong, and impervious to wet. Until the rushes die and drop the nest remains securely fastened to them, and in winter affords a safe and comfortable retreat to the small reed-frogs, of which sometimes as many as three or four are found living in one nest. The interior is very thickly lined with feathers; the eggs are three, pear-shaped, and a bright, beautiful blue colour, sometimes with a slight greenish tinge. The bird is so abundant in extensive marshes that I have on several occasions, during a day's ramble, found as many as forty or fifty nests, sometimes a dozen or more being placed close together, but I have never taken more than three eggs from one nest. I mention this because I have seen it stated that four or five eggs are sometimes found. I trust that no reader of this sketch imagines that I robbed all the eggs contained in so many nests. I did nothing so barbarous, although it is perhaps "prattling out of fashion" to say so; but with the destructive, useless egg-collecting passion I have no sympathy. By bending the pliant rushes downwards the eggs can be made to roll out into the hand; and all those which I thus took out to count were, I am glad to say, put back in their wonderful cradles. I had a special object in examining so many nests. A gaucho boy once brought me a nest which had a small circular _stopper_, made of the same texture as the body of the nest, attached to the aperture at the _side_, and when swung round into it fitting it as perfectly as the lid of the trap-door spider fits the burrow. I have no doubt that it was used to close the nest when the bird was away, perhaps to prevent the intrusion of reed-frogs or of other small birds; but I have never found another nest like it, nor have I heard of one being found by any one else; and that one nest, with its perfectly-fitting stopper, has been a puzzle to my mind ever since I saw it. 189. LEPTASTHENURA ÆGITHALOIDES (Kittl.). (TIT-LIKE SPINE-TAIL.) +Synallaxis ægithaloides+, _Burm. La-Plata Reise_, ii. p. 469 (Mendoza); _Hudson, P. Z. S._ 1872, p. 544 (Rio Negro). +Leptasthenura ægithaloides+, _Scl. et Salv. P. Z. S._ 1869, p. 632 (Buenos Ayres); _iid. Nomencl._ p. 63; _Durnford, Ibis_, 1877, p. 180 (Buenos Ayres), et 1878, p. 396 (Centr. Patagonia); _Gibson, Ibis_, 1880, p. 30 (Buenos Ayres); _White, P. Z. S._ 1882, p. 611 (Catamarca); _Barrows, Bull. Nutt. Orn. Cl._ viii. p. 206 (Entrerios).