28 



ISLAND LIFE 



PART I 



fruit-eating birds, almost equally abundant in tropical Asia 

 and Africa, but less plentiful in America, where they 

 probably suffer from the competition of the larger sized 

 toucans. The genera of each country are distinct, but all 

 are closely allied, the family being a very natural one. The 

 trogons form a family of very gorgeously coloured and 

 remarkable insect-eating birds very abundant in tropical 

 America, less so in Asia, and with a single genus of two 

 species in Africa. 



Among reptiles we have two families of snakes — the 

 Dendrophida) or tree-snakes, and the Dryiophid(3e or green 

 whip-snakes — which are also found in the three tropical 

 regions of Asia, Africa, and America, but in these cases 

 even some of the genera are common to Asia and Africa, 

 or to Africa and America. The lizards forming the family 

 Amphisb9enida3 are divided between tropical Africa and 

 America, a few species only occurring in the southern 

 portion of the adjacent temperate regions ; while even the 

 peculiarly American family of the iguanas is represented 

 by two genera in Madagascar, and one in the Fiji and 

 Friendly Islands. Passing on to the Amphibians the 

 worm-like Coeciliadse are tropicopolitan, as are also the 

 toads of the family Engystomatida^. Insects also furnish 

 some analogous cases, three genera of Cicindelidoe, 

 (Pogonostoma, Ctenostoma, and Peridexia) showing a 

 decided connection between this family in South America 

 and Madagascar ; while the beautiful family of diurnal 

 moths, Uraniida?, is confined to the same two countries. 

 A somewhat similar but better known illustration is 

 afforded by the two genera of ostriches, one confined to 

 Africa and Arabia, the other to the plains of temperate 

 South America. 



General features of Overlapping and Discontinuous 

 Areas. — These numerous examples of discontinuous genera 

 and families form an important section of the facts of 

 animal dispersal which any true theory must satisfactorily 

 account for. In greater or less prominence the}^ are to be 

 found all over the world, and in every group of animals, 

 and they grade imperceptibly into those cases of conter- 

 minous and overlapping areas which we have seen to 



