At the same time the boreal Atlantic and Pacific have their peculiar forms. Thus the European and American Lobsters are confined to the Atlantic, while the North Pacific possesses a very rich array of Lithodinae, which cannot be paralleled in the Atlantic. We may explain the community of many littoral forms to both the North Atlantic and Pacific coasts by the continuous coast-line uniting them, which in former times possibly did not lie so far north, or else was not subjected to so rigorous a climate as now. In the =Antarctic= zone we are presented with very different relations, since the great continents are drawn out to points towards the south, and are isolated by vast tracts of intervening deep sea. Nevertheless, certain littoral forms are circumpolar, _e.g._ the Palinurid _Iasus_ and the Crabs _Cyclograpsus_ and _Hymenosoma_. The genus _Dromidia_ is common to Australia and South Africa, though it is apparently absent from South America. The Isopod genus _Serolis_ is confined to Antarctic seas. The majority are littoral species, and they are distributed round the coasts of Patagonia, Australia, and Kerguelen in a manner that certainly suggests a closer connection between these shores in the past. These facts are, on the whole, evidence in favour of the former existence of an Antarctic continent stretching farther north and connecting Australia, Africa, and S. America—a supposition that has been put forward to account for the distribution of the Penguins, Struthious birds, Oligochaets, Crayfishes, etc., in these regions (see pp. 215–217).