522 
GEOGRAPHICAL ZOOLOGY. 
[part IV. 
Family 30— HELICINID^. (7 Genera, 433 Species.) (1868.) 
General Distribution. 
Neotropical 
Ne ARCTIC 
P ALAS ARCTIC 
Ethioptan 
Oriental 
Australian 
Sub-regions. 
Sub-regions. 
Sub- regions. 
Sub-regions. 
Sub-regions. 
St:b-rkl.ions, 
— 2 . 3.4 
| 3 - 
1 
— 
| 3.4 
1 . 2 . 3 - 
The Helicinidee are very characteristic of the Antilles, com- 
paratively few being found in any other part of the world 
except the Islands- of the Pacific. The genera are : — 
Trochatella (33 sp.), Antilles with a species in Venezuela, and 
another in Cambodj a ; Lucidella (5 sp.), Antilles; Helicina{ 274 
sp.), Antilles, Pacific Islands, Tropical America, Southern 
United States, Moluccas, Australia, Philippines, Java, Andaman 
Islands and North China ; Schasicheila (5 sp.), Mexico, Guate- 
mala and Bahamas; Alcadia (28 sp.), Antilles; Georissa (5 sp.) 
Moulmein to Burmah. About 10 per cent, of new species 
appear to have been since described in the larger genera of this 
family. 
General Observations on the Distribution of the Land Mollusca. 
A consideration of the distribution of the families and genera 
of land-shells shows us, that although they possess some special 
features, yet they agree in many respects with the higher animals 
in their limitation by great natural barriers, such as oceans, 
deserts, mountain ranges, and climatal zones. A remarkable 
point in the distribution of these animals, is the number of 
genera which have a very limited range, and also the prevalence 
of genera having species scattered, as it were at random, all 
over the earth. No less than 14 genera (or about one-sixth of 
the whole number) are confined to the Antilles, while the 
greater part of the sub-genera of modern authors are restricted to 
limited areas. 
If we first compare the New World with the Old, we find the 
difference as regards genera quite as great as in most of the 
