The common hare appears to have been introduced into Orkney by a Mr Moodie of Melsetter, early in the eighteenth century, but both that attempt at acclimatisation and one by Malcolm Laing, the historian, in 1818, proved comparative failures. Better success, however, attended the efforts of Mr Samuel Laing and Mr Baikie of Tankerness about 1830, and at the present day, hares are found in the Mainland, Rousay, Eday, Shapinsay, Hoy, and South Ronaldshay. The white hare occurred in Hoy at an early date, as recorded by Jo Ben, a resident in Orkney, in his _Descriptio Insularum Orchadiarum_, in 1529:—“Albi lepores hic sunt, et capiuntur canibus.” It died out, however, and has only recently been reintroduced. The rabbit is common throughout the Islands. Of other and less desirable rodents, the black rat was once general in South Ronaldshay, and probably still occurs there. The brown rats, common in most parts of Orkney, have been known at times to forsake certain islands altogether, taking to the sea in a body in search of a new home. The field mouse, and the house mouse are universal. The common field vole is plentiful in most of the islands, and there is a doubtful record of the water vole from Hoy. _Microtus orcadensis_, or the Orkney vole discovered in 1904, is a highly interesting species peculiar to Orkney and certain parts of Shetland. The common shrew has been found in Walls and Orphir, and the water shrew in Walls. Bats are rare in Orkney, but occurrences of _vesperugo pipistrellus_ have been recorded from Walls, Sanday, and Kirkwall, of _vespertilio murinus_ from Walls; while there is an interesting but doubtful record of a specimen of _vesperugo noctula_ having been captured in South Ronaldshay. Appearances of the walrus in Orkney waters have been recorded from Eday, Hoy Sound, and Walls at various dates from 1825 to 1864; and Orkney seals include _phoca vitulina_, which breeds on several islands and skerries, _phoca groenlandica_, and the grey seal. The occurrence of the hooded seal is doubtful. Among Cetacea, the Greenland and sperm whales are rare visitors, the hump-backed whale, still rarer; but the common rorquall, Sibbald’s rorquall, the lesser rorquall, the beaked whale, the grampus, the common porpoise, and the white-sided dolphin are all fairly common. The bottlenose is, however, _the_ Orkney whale, occurring at times in schools of 500 in number. The bottlenosed dolphin and the white-beaked dolphin are also on record.