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Show 24 ISLAND LIFE. [PART I. area completely separated from the others. ' The most n~rthe~ly is 0. tricarunc1tlatus of Gosta Rica and Veragua., a brown b1rd w1th a white head and three long caruncles growing upwards at the base of the beak. Next comes 0. variegatus, in Venezuela, a white bird with a brown bead and numerous caruncles on the throat, 'perhaps conterminou·s w'ith t\le last; in Guiana, extending to near the mouth of the Rio Negro, we have 0. nive~ts, the bell-bird described by Waterton, which is pure white, with a single long fleshy caruncle at the · base of the beak ; the last species, 0. nudicollis, inhabits South-east Brazil, and is also white, but with black stripes over the eyes, and with a naked throat. These birds are about the size of thrushes and are all remarkable for their loud-ringing notes like a bell or a blow on an anvil, as well as for their peculiar colours. They are therefore known to the native Indians wherever they exist, and we may be the more sure that they do not spreau over the intervening areas where they have never been found, and where the natives know nothing of them. A good example of isolated species of a group nearer home, is afforded by the snow-partridges of the genus Tetraogallus. ·One species inhabits the Caucasus range and nowhere else, keeping to the higher slopes from 6,000 to 11,000 feet above the sea, and accompaning the ibex in its wanderings, as both feed on the same plants. Another has a wider range in Asia Minor and Persia from the Taurus mountains to the South-east corner of the Caspian Sea ; a third species inhabits the Western Himalayas, between the forests and perpetual snow, extending eastwards to Nepal, while a fourth is found on the north side of the mountains in Thibet, and the ranges of these two perhaps overlap ; the last species inhabit the Altai mountains, and like the two first appears to be completely separated from all its allies. There are some few still more extraordinary cases in which the species of one genus are separated in remote continents or islands. The most striking of these is that of the tapirs, forming the genus Tapirus, of which there are two or three species in South America, and one very distinct species in Malacca and Borneo, separated by nearly half the circumference of the globe. Another example among quadrupeds is a peculiar genus of moles cHAP. 11.] THE ELEMI~NTARY FACTS OF DISTRIBUTIGN. 25 named Urotrichus, of which one species inhabits Japari and the other British Columbia. The cuckoo-like honey-guides, forming the genus Indicator, are tolerably abundant in tropical Africa, but there are two outlying species, one in the Eastern Himalaya mountains, the other in Borneo, both very rare, and quite recently an allied species has been found in the Malay peninsula. The beautiful blue and green thrush-tits forming the genus Cochoa, have two species in the Eastern Himalayas, while the third is confined to Java; the curious genus Eupetes, supposed to be allied to the dippers, has two species in Sumatra, and the other species two thousand miles distant in New Guinea ; lastly, the lovely ground-thrushes of the genus Pitta, range from Hindostan to Australia, while a single species, far removed from all its near allies, inhabits West Africa. Pecruliarities of Generic and Family Distribution.-The exam pies now given sufficiently illustrate the mode in which the several species of a genus are distributed. We have next to consider genera as the component parts of families, and families of orders, from the same point of view. AU the phenomena presented by the species of a genus are reproduced by the genera of a family, and often in a more marked degree. Owing, however, to the extreme restriction of genera by modern naturalists, there are not many among the higher amimals that have a world-wide distribution. Among the mammalia there is no such thing as a truly cosmopolitan genus~ This is owing to the absence of all the higher orders except the mice from Australia, while the genus Mus, which occurs there, is represented by a distinct group, Hesperomys, in America. If, however, we consider the Australian dingo as a native animal we might class the genus Canis as cosmopolite, but the wild dogs of South America are now formed into separate genera by some naturalists. Many genera, however, range over three or more continents, as Felis (the cat genus) absent only from Australia; Ursus (the bear genus) absent from Australia and tropical Africa; Cervus (the deer genus) with nearly the same range; and Sciurus (the squirrel genus) found in all the continents but .Australia. Among birds Turdus, the thrush, and Hirundo, the swallow genus, are the only perching |
