556. Biziura lobata Vol. VII. Pl. 18. Family LARIDÆ, _Leach_. Genus LARUS, _Linn._ The members of this genus are distributed over the sea-shores of every part of the globe. Only one species inhabits Australia, to which country it is confined, and where it represents the _Larus marinus_ of Europe and America. 557. Larus Pacificus Vol. VII. Pl. 19. Genus XEMA, _Leach_. A genus of Gulls, the members of which are delicate in their structure, elegant in their appearance, and graceful in all their actions. Many species are found in Europe and America, and others inhabit Africa; one species only has been characterized as Australian, but I believe that another will be found in Torres’ Straits very similar to, but much larger than, the _X. Jamesonii_ of the southern parts of that continent. 558. Xema Jamesonii Vol. VII. Pl. 20. Subfamily ——? Genus LESTRIS, _Ill._ The high latitudes of both the northern and southern hemispheres are frequented by parasitic Gulls. One species of this form has been found in the Australian seas, and another has been discovered within the Antarctic circle. 559. Lestris Catarractes Vol. VII. Pl. 21. Although I have figured and described this Australian bird as identical with the Skua Gull of Europe, it is likely that hereafter reasons may be found for separating them. In a letter just arrived from Mr. J. M’Gillivray, dated on board H.M.S. Rattlesnake, Feb. 6, 1848, that gentleman says, “The _Lestris Catarractes_ was noticed on various occasions in different parts of the South Indian Ocean; while off the Cape of Good Hope a solitary individual and subsequently two in company were seen. I have observed it following and hovering over a bait towing astern, and once saw it chase a Cape Petrel and force it to alight on the water. This bird seldom remained with us for more than half an hour at a time, during which it made a few circular flights about the ship.” Subfamily STERNINÆ, _Bonap._ The members of this family inhabiting Australia and Europe are nearly equal in number, and in each country examples of the same forms are found to exist; the Australian fauna has also a _Gygis_ and an _Onychoprion_ neither of which inhabit the European seas, and four species of _Anoüs_, of which only one frequents the northern hemisphere. Genus SYLOCHELIDON, _Brehm_. 560. Sylochelidon strenuus Vol. VII. Pl. 22. A representative of the _S. Caspius_ of Europe. Genus THALASSEUS, _Boie_. The members of this genus, the type of which is the _T. Cantiacus_ of the British Islands, are widely dispersed over most parts of the Old World, and three distinct species inhabit Australia.