CHAP, xrx THE MADAGASCAR GROUP 439 



the boa family, and forms a peculiar and very distinct 

 genus, Casaria, whose nearest allies seem to be the Ungalia 

 of Cuba and Bolyeria of Australia. It is hardly possible 

 to believe that this serpent has very long maintained 

 itself on so small an island ; and though we have no record 

 of its existence on Mauritius, it may very well have 

 inhabited the lowland forests without being met with by 

 the early settlers ; and the introduction of swine, which 

 soon ran wild and effected the final destruction of the 

 dodo, may also have been fatal to this snake. It is, how- 

 ever, now almost certainly confined to the one small islet, 

 and is probably the land-vertebrate of most restricted 

 distribution on the globe. 



On the same island there is a small lizard, Scelotes 

 hojeri, recorded also from Mauritius and Bourbon, though 

 it appears to be rare in both islands ; but a gecko, Phelsuma 

 guenthcri, is restricted to the island. As Round Island is 

 connected with Mauritius by a bank under a hundred 

 fathoms below the surface, it has probably been once 

 joined to it, and when first separated would have been 

 both much larger and much nearer the main island, 

 circumstances which would greatly facilitate the trans- 

 mission of these reptiles to their present dwelling-place, 

 where they have been able to maintain themselves owing 

 to the complete absence of competition, while some of them 

 have become extinct in the larger island. 



Flora of Madagascar and the Mascarene Islands. — The 

 botany of the great island of Madagascar has been perhaps 

 more thoroughly explored than that of the opposite coasts 

 of Africa, so that its peculiarities may not be really so 

 great as they now appear to be. Yet there can be no 

 doubt of its extreme richness and grandeur, its remark- 

 able speciality, and its anomalous external relations. It 

 is characterised by a great abundance of forest-trees and 

 shrubs of peculiar genera or species, and often adorned 

 with magnificent flowers. Some of these are allied to 

 African forms, others to those of Asia, but of the two 

 affinities the former greatly preponderates. There 

 are also, as in the animal world, some decided South 

 American relations, while other groups point to Australia, 

 or are altogether isolated. 



