472 Habits and Structure of the Anaspidida, ete. 
also to the coldest parts of the temperate zone, the majority of the 
Anaspidacea and Phreatoicide being found at considerable elevations on 
mountain ranges which are covered with snow for at any rate a great part 
of the winter. They are absolutely unknown from Australia north of the 
Dividing Range. 
A great deal of evidence has accumulated in recent years supporting the 
theory of the existence, perhaps in very early Tertiary times, of an Antarctic 
continent, affording means of communication between Southern Australia, 
South America, and to a less extent with New Zealand, upon which the 
characteristically temperate part of the fauna and flora now found, with many 
elements shared in common in these countries, was largely developed. The 
greatest community exists now between temperate Southern Australia and 
South America, the connection with New Zealand being apparently more 
ancient. | 
If this Antarctic Continent really existed, it is fairly certain that the 
Anaspidacea and Phreatoicide, being not only temperate but alpine in their 
habitat, formed a part of its fauna; we should therefore be justified in 
expecting the discovery of these creatures or nearly related forms in 
temperate South America, especially as the Phreatoicide have already been 
found in New Zealand. 
[Note added while the paper was passing through the press.—Certain other 
Crustacea that were commonly met with in the fresh-waters of Tasmania, 
especially in the highlands, have closely related forms in New Zealand and 
South America. Thus the Amphipod Chiltonia australis is exceedingly 
common in Tasmania, the genus being represented in South Victoria and 
New Zealand, and replaced in South America by the closely-related Hyalella. 
The commonest element in the plankton of the lakes and tarns of Tasmania 
is afforded by various species of the Copepod genus Leckella, which entirely 
replaces the northern Diaptomus. Beckella occurs again in New Zealand and 
temperate South America, but is unknown in the northern hemisphere. Other 
species of fresh-water Crustacea are closely related to forms in the northern 
hemisphere, but it seems very probable that they have reached Tasmania. 
and Southern Australia vid South America and the Antarctic continent. 
Such are the genera Neoniphargus and Gammarus, which are unknown in the 
tropics, and confined in their distribution to the temperate northern hemi- 
sphere and to temperate Australasia. The small planktonic genus Bosmina, 
which is widely distributed over the northern hemisphere and descends right 
down the Andes to temperate South America, was found by me as a common 
constituent of the plankton of the highland lakes in Tasmania. The genus 
