This bird does not inhabit Van Diemen’s Land, but is universally dispersed among the sedgy sides of rivers and lagoons, both in South Australia and New South Wales; I also observed it in great abundance on the banks of all the rivers to the northward of Liverpool Plains in all these localities; it is strictly migratory, arriving in September and departing again before the commencement of winter. In its general economy it closely resembles its European congeners, but possesses a still louder and more melodious song, which it is continually pouring forth and which tends much to enliven the monotony of the parts frequented by it. It is rather a late breeder, scarcely ever beginning this natural duty before the month of November. The nest, like that of the Reed Warbler of Europe, is suspended from two or three reeds at about two feet above the surface of the water, and is composed of the soft skins of reeds and dried rushes. The eggs, which are four in number, ten lines long by seven lines broad, are of a greyish white, thickly marked all over with irregular blotches and markings of yellowish brown, umber brown and bluish grey, intermingled together without any appearance of order or arrangement. The food consists of insects of various kinds. The sexes are so precisely alike that dissection must be resorted to to distinguish them. All the upper surface olive-brown; wings and tail brown, margined with olive-brown; all the under surface tawny or deep buff, fading into white on the throat; under mandible fleshy white, remainder of the bill and the legs olive horn-colour; irides brown. The figure is of the natural size. [Illustration: ACROCEPHALUS LONGIROSTRIS: _Gould_. _J. Gould and H. C. Richter del et lith._ _Hullmandel & Walton Imp._ ] ACROCEPHALUS LONGIROSTRIS, _Gould_. Long-billed Sedge-Warbler. _Calamoherpe longirostris_, Gould in Proc. of Zool. Soc., Part XIII. p. 20. _Gooȑ-jee-gooȑ-jee_, Aborigines of the lowland districts of Western Australia. The present bird, which I have designated _longirostris_, is the largest of the two species of _Acrocephalus_ known to inhabit Australia.