Vil THE LOST ANTARCTICA 22 F/ 
northern Miphargus and Gammarus, but grading almost completely 
into the latter. Both Miphargus and Gammarus are absolutely 
unknown from the tropics, but whether, like Losmina, they occur 
in the Andes and temperate South America is not known; it 
seems, however, probable that they have reached Southern 
Australia by way of South America rather than through the 
tropics of Asia and Australia, where there is no range of 
mountains to permit the migration of a group of animals 
apparently dependent on a temperate climate. The other 
common fresh-water Amphipod in temperate Australia and New 
Zealand is Chiltonia, whose nearest ally is Hyalella from Lake 
Titicaca on the Andes, and temperate South America. 
The Anaspidacea and Phreatoicidae, which are so characteristic 
of temperate Australia, and are generally of an Alpine habit, 
have never been found in South America, but the Anaspidacea 
are represented by numerous marine forms in the Permian and 
Carboniferous strata of the northern hemisphere, so that it is 
probable that this group reached the southern hemisphere from 
the north through America. 
The distribution of the fresh-water Crustacea, therefore, in the 
temperate southern hemisphere affords strong evidence in favour 
of the view that the chief land-masses of this hemisphere, which 
are at present separated by such vast stretches of deep ocean, 
were at no very remote epoch connected in such a way as to 
permit of an intermixture of the temperate fauna of New Zealand, 
Australia, and South America. While this connexion existed, 
a certain number of forms characteristic of the northern hemi- 
sphere, which had worked through the tropics by means of the 
Andes, were enabled to reach temperate Australia and New 
Zealand. The existence of a coast-line connecting the various 
isolated parts of the southern hemisphere would, of course, also 
account for the community which exists between their httoral 
marine fauna. It is impossible to enter here into the nature of 
this land-connexion which is becoming more and more a necessary 
hypothesis for the student of geographical distribution, whatever 
group of animals he may choose, but it may be remarked that the 
connexion was probably by means of rays of land passing up from 
an Antarctic continent to join the southernmost projections of 
Tierra del Fuego, Tasmania, and New Zealand. 
