The geographical distribution of animals, with a study of the relations ...

446 ZOOLOGICAL GEOGRAPHY. [part hi.The aquatic birds and waders all belong to wide-spreadgenera, and only one or two are peculiar species."The Sandwich Islands thus possess a larger proportion ofpeculiar genera and speciesof land-birds than any other groupof islands, and they are even more strikingly characterised bywhat seems to be a peculiar family. The only other class ofterrestrial animals at all adequately represented on these islands,are the land shells ;and here too we find a peculiar family, subfamily,or genus (Achatinella or Achatinellidse)consisting of anumber of genera, or sub-genera,— according to the divergent viewsof modern conchologists,—and nearly 300 species. The Eev. J.T. Gulick, who has made a special study of these shells on thespot, considers that there are 10 genera, some of which are confinedto single islands. The species are so restricted that theiraverage range is not more than five or six square miles, whilesome areconfined to a tract of only two square miles in extent,and very few range over an entire island. Some species areconfined to the mountain ridges, others to the valleys ;and eachridge or valley possesses its peculiar species. Considerablymore than half the species occur in the island of Oahu, wherethere is a good deal of forest. Very few shells belonging toother groups occur, and they are all small and obscure ; theAchatinellse almost monopolising the entire archipelago.Remarks on the probable past history of the Sandwich Islands.—The existence of these peculiar groups of birds and landshellsin so remote a group of volcanic islands, clearly indicatesthat they are but the relics of a more extensive land ; and thereefs and islets that stretch for more than 1,000 miles in a westnorth-westdirection, may be the remains of a country oncesufficiently extensive to develope these and many other, nowextinct, forms of life. 1Some light may perhaps be thrown on the past history of the1A new genus of Beetles (Apterocyclus) of the family Lucanidse, hasrecently been described from the Sandwich Islands, and it is said to be mostnearly related to a group inhabiting Chih,—an indication either of the greatantiquity of the fauna, or of the varied accidental migrations from which ithas had its origin.