304 
ISLAND LIFE. 
[part it. 
This difference is so remarkable that it is worth stating in a 
comparative form : — 
Inoperculata. Operculata. Auriculid®. 
Sandwich Islands 332 5 9 
Rest of Pacific Islands 200 115 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 lime- 
stone, which is plentiful in both these areas, is especially favour- 
able to them, while the purely volcanic rocks are especially 
unfavourable. The other peculiarities of the Sandwich Islands, 
however, such as the enormous preponderance of the strictly 
endemic Achatinellinse, 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 Carelia and Catinella with eight 
species are peculiar to the island of Kaui; Bulimella, Apex, 
Frickella, and Blauneria, to Oahu ; Perdicella to Maui ; and Ebur- 
nella to Lanai. The Bev. John T. Gulick, who has made a 
special study of the Achatinellinae, 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.” Proceedings of the 
Zoological Society of London , 1873, p. 80. “ On the Classification of the 
Achatinellidse.” 
