CHAP. XIX THE MADAGASCAR GROUP 429 



which sixteen are peculiar to the islands, twenty-one are 

 found also in Madagascar, and three found in Africa and 

 not in Madagascar; while of the peculiar species, six 

 belong to Madagascar or Mascarene genera. A species of 

 Chameleon is also peculiar to the islands. 



These facts point to the conclusion that tlie Comoro 

 Islands have been formerly more nearly connected with 

 Madagascar than they are now, probably by means of 

 intervening islets and the former extension of the latter 

 island to the westward, as indicated by the extensive 

 shallow bank at its northern extremity, so as to allow of 

 the easy passage of birds, and the occasional transmission 

 of small mammalia by means of floating trees.^ 



The Seychelles Archipelago. — This interesting group 

 consists of about thirty small islands situated 700 miles 

 N.N.E. of Madagascar, or almost exactly in the line formed 

 by continuing the central ridge of that great island. The 

 Seychelles stand upon a rather extensive shallow bank, the 

 100-fathom line around them enclosing an area nearly 200 

 miles long by 100 miles wide, while the 500-fathom line 

 shows an extension of nearly 100 miles in a southern 

 direction. All the larger islands are of granite, with 

 mountains rising to 3,000 feet in Mahe, and to from 1,000 

 to 2,000 feet in several of the other islands. We can 

 therefore hardly doubt that they form a portion of the 

 great line of upheaval which produced the central granitic 

 mass of Madagascar, intervening points being indicated by 

 the Amirantes, the Providence, and the Farquhar Islands, 

 which, though all coralline, probably rest on a granitic 

 basis. Deep channels of more than 1,000 fathoms now 

 separate these islands from each other, and if they were 

 ever sufficiently elevated to be united, it was probably at a 

 very remote epoch. 



The Seychelles may thus have had ample facilities for 

 receiving from Madagascar such immigrants as can pass 

 over narrow seas ; and, on the other hand, they were 

 equally favourably situated as regards the extensive Saya 

 de Malha and Cargados banks, which were probably once 



^ For the birds of the Comoro IsLancIs see Proc. Zool. Soc, 1877, p. 295, 

 and 1879, p. 673. 



