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Show 396 ISLAND LIFE. (rART II. probably inhabited Europe, which at that epoch enjoyed a subtropical climate ; and this is rendered almost certain by the discovery in the Miocene of France of fossil remains of trogons and jungle-fowl. If, then, these Indian birds date back to the very period during which alone Lemuria could have existed, that continent was quite unnecessary for their introduction into :Madagascar, as they could have followed the same track as the mammalia of Miocene Europe and Asia ; w bile if, as I maintain, they are of more recent date, then Lemuria had ceased to exist, and could not have been the means of their introduction. MAP OF THE INDIAN OOEAN. Showing the position of banks less than 1.0~0 fathoms deep between Africa and the Indian Pemnsula. Submerged I~lands between Madagascar and Ind,ia.-Looking at the accompanymg map of the Indian Ocean, we see that ootween Madagascar and India there are now extensive shoals and coralreefs, such as are always held to indicate subsidence· and we may therefore fairly postulate the .former existenc: here of several large islands, some of them not much inferior to Mada.gascar itself. These reefs are all separated from each other by CHAP. XIX.] THE MADAGASCAR GROUP. 397 very deep sea-much deeper than that which divides Madagascar from Africa, and we have therefore no reason to imagine their former union. Bnt they would nevertheless greatly facilitate the introduction of Indian birds into the Mascarene Islands and Madagascar; and these facilities existing, such an immigration would be sure to take place, just as surely as American birds have entered the Galapagos and Juan Fernandez, as European birds now reach the Azores, and as Australian birds reach such a distant island as New Zealand. This would take place the more certainly because the Indian Ocean is a region of violent periodical storms at the changes of the monsoons, and we have seen in the case of the Azores and Bermuda how important a factor this is in determining the transport of birds across the ocean. Mr. Darwin's theory of the formation of atolls is rrow almost univE:>rsally accepted as the true one, and this theory implies that the areas in question are still, or have very recently been, subsiding. The final disappearance of these now sunken iRlands does not, therefore, in all probability, date back to a very remote epoch; and this exactly accords with the fact that some of the birds, as well as the fruit-bats of the genus Pteropus, are very closely allied to Indian species, if not actually identical, others being distinct species of the same gen€lra. The fact that not one closely-allied species or even genus of Indian or Malayan mammals is found in Madagascar, sufficiently proves that it is no land-connection that has brought about this small infusion of Indian birds and bats; while we have sufficiently shown that when we go back to remote geological times no land-conn~cti01~ in this direction was necessary to explain the phenomena of the distribution of the Lemurs and Insectivora. A land-connection with some continent was undoubtedly necessary, or there would have been no mammalia at all in Madagascar; and the nature of its fauna on the whole, no less than the moderate depth of the intervening strait and the comparative approximation of the opposite shores, clearly indicate that the connection was with Africa. Concluding remarks on "Lem~tria."-I have gone into this question in some detail, because Dr. Hartlaub's criticism on my |