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Show 304 ISLAND LIFE. [PART IT. This difference is so remarkable that it is worth stating in a comparative form :- lnopcrculata. Sandwich Islands ........................ 332 Rest of Pacific Islands .................. 200 Operculata. 5 115 Auricu'ido.e. 9 16 When we remember that in the West Indian Islands the Operculata abound in a greater proportion than. even in. the Pacific Islands generally, we are led to the conclusiOn that limestone, which is plentiful in both these areas, is especially fav.ourable to them, while the purely volcanic rocks are especmlly unfavourable. The other peculiarities of the Sandwich Islands, however, such as the enormous preponderance of the strictly endemic Achatinellinre, and the presence of genera which occur elsewhere only beyond the Pacific area in various parts of the great continents, undoubtedly point to a very remote origin, at a time when the distribution of many of the groups of mollusca was very different from that which now prevails. A very interesting feature of the Sandwich group is the extent to which the species and even the genera are confined to separate islands. Thus the genera CarBlia and Catinella with eight species are peculiar to the island of Kaui; Bulimella, Apex, :Frickella, and Blauneria, to Oahu ; Perdicella to Maui ; and Eburnella to Lanai. The Rev. John T. Gulick, who has made a special study of the Achatinellinre, informs us that the average range of the species in this sub-family is five or six miles, while some are restricted to but one or two square miles, and only very few have the range of a whole island. Each valley, and often each side of a valley, and sometimes even every ridge and peak possesses its peculiar species.1 The island of Oahu, in which the capital is situated, has furnished about half the species already known. This is partly due to its being more forest clad, but also, no doubt, in part to its being better explored, so that notwithstanding the exceptional riches of the group, we have no reason to suppose that there are not many more species to be 1 Journal of the Linnean Society, 1873, p. 496. "On Diversity of Evolution under one set of External Conditions." P1·oceedings of the Zoological Society of London, 1873, p. 80. "On the Classification of the ,Achatinellidre. '' CHAP. XV.] 'l'IIE SAND\VICTI ISLANDS. 305 found in the less explored islands. Mr. Gulick tells us that the forest region that covers one of the mountain ranaes of 0 Oahu is about forty miles in length, and five or six miles in width, yet this small territory furnishes about 175 species of Achatinellidre, represented by 700 or 800 varieties. The most important peculiar genus, not belonging to the Achitinella group, is Carelia, with six species and several named varieties, all peculiar to Kaui, the most westerly of the large islands. This would seem to show that the small islets stretching westward, and situated on an extensive bank with less than a thousand fathoms of water over it, may indicate the position of a large submerged island whence some portion of the Sandwich Island fauna was derived. Insects.-Unfortunately we have as yet no such knowledge of the insects of these islands as we possess in the case of the Azores and St. Helena, but some considerable collections have been sent over by Mr. T. Blackburn, now resident there, and we may therefore soon possess fuller and more accurate information. Although insects are said to be very scarce, yet all the chief tribes of Coleoptera appear to be represented, though as yet by very few species. These appear to be for the most part peculiar, but to have widespread affinities. The majority, as might be expected, are allied to Polynesian, Australian, or Malayan forms; some few are South American (perhaps introduced), while others show north temperate affinities. There are several new genera, and one peculiar group of six species is said to form a new family allied to the Anthribiclre. A new genus of Lucanidre is said to be allied to a Chilian genus. If we consider the greater facilities of insects for dispersal when compared with birds or land-shells, the characteristics of the insect fauna, so far as yet known, are sufficiently in harmony with the amount of speciality and isolation presented by the latter groups. Vegetation of the Sandwich Islands.-The flora of these islands is in many respects so peculiar and remarkable, and so well supplements the information derived from its interesting but scanty fauna, that a brief account of its more striking features will not be out of place; and we fortunately have a pretty full knowledge of it, owing to the researches of the American botanist X |
