FORMER CONTINENT. 67 



it prolDable that in the Tertiary period the Indian Ocean 

 was occupied in part by a continent or archipelago, of 

 which we have relics in Madagascar and the Mascarene 

 Islands, the Seychelles, Amirante, and Chagos groups, and, 

 nearer to India, the Maldive and Laccadive groups, all of 

 which have encircling reefs, a fact which has not been much 

 noticed, but which, from Mr. Darwin's researches on the 

 subject of the formation of coral, indicates that these islands 

 are still sinking land. But he also contends that both 

 Madao-ascar and the Mascarene and Comoro Islands must 

 have been connected with Africa in some Tertiary geological 

 epoch, probably while the Sahara was still a shallow sea- 

 bottom, and before the incursion of the numerous ungulate 

 animals and the larger felines from the Asiatic continent. 

 A bank of soundings now existing in the Mozambique 

 Channel reduces the width of that strait from 230 miles, its 

 present narrowest wddth, to 160 miles, clearly indicating a 

 former closer connection between the island and the continent. 

 The Mascarene Islands probably represent the portion of land 

 which was separated earliest, before any carnivora had reached 

 the country. The lemuride type of animals evidently existed 

 in Africa at that period, but has since become almost extinct, 

 excepting the Galagos, a family of the Lemuridse which are 

 not very nearly aUied to the lemuride forms now found in 

 Madagascar, These latter, probably from long isolation, have 

 become modified into many exceptional and peculiar species, 

 especially as they have been free from the attacks of all 

 large carnivora. The small insectivora are probably relics 

 of a much more extensive fauna of that order of mammals, 

 which was greatly developed in the early Tertiary epochs. To 

 the fact of the long isolation of Southern Africa from the 

 Oriental region and fauna is probably also due the develop- 

 ment of the struthious or ostrich type of birds in the southern 

 continents of South Africa, South America, and Australia, as 

 well as of birds of other families also incapable of flight. 

 "Free from the incursions of destructive felines, the dodo and 

 other birds flourished in Mauritius and Eodriguez, and the 

 huge ^pyornis in Madagascar, while the gigantic tortoises, 

 now only left in Aldebra, an uninhabited island, were also 



