446 ZOOLOGICAL GEOGRAPHY. [PART HI. 
The aquatic birds and waders all belong to wide-spread 
genera, and only one or two are peculiar species. 
The Sandwich Islands thus possess a larger proportion of 
peculiar genera and species of land-birds than any other group 
of islands, and they are even more strikingly characterised by 
what seems to be a peculiar family. The only other class of 
terrestrial animals at all adequately represented on these islands, 
are the land shells; and here too we find a peculiar family, sub- 
family, or genus (Achatinella or Achatinellide) consisting of a 
number of genera, or sub-genera,— according to the divergent views 
of modern conchologists,—and nearly 300 species. The Rev. J. 
T. Gulick, who has made a special study of these shells on the 
spot, considers that there are 10 genera, some of which are con- 
fined to single islands. The species are so restricted that their 
average range is not more than five or six square miles, while 
some are confined to a tract of only two square miles in extent, 
and very few range over an entire island. Some species are 
confined to the mountain ridges, others to the valleys; and each 
ridge or valley possesses its peculiar species. Considerably 
more than half the species occur in the island of Oahu, where 
there is a good deal of forest. Very few shells belonging to 
other groups occur, and they are all small and obscure; the 
Achatinelle almost monopolising the entire archipelago. 
Remarks on the probable past history of the Sandwich Islands. 
—The existence of these peculiar groups of birds and land- 
shells in so remote a group of volcanic islands, clearly indicates 
that they are but the relics of a more extensive land; and the 
reefs and ‘islets that stretch for more than 1,000 miles in a west- 
north-west direction, may be the remains of a country once 
sufficiently extensive to develope these and many other, now 
extinct, forms of life.t 
Some light may perhaps be thrown on the past history of the 
1 A new genus of Beetles (Apterocyclus) of the family Lucanide, has 
recently been described from the Sandwich Islands, and it is said to be most 
nearly related to a group inhabiting Chili,—an indication either of the great 
antiquity of the fauna, or of the varied accidental migrations from which it 
has had its origin, 
