CHAP. XIX THE MADAGASCAR GROUP 418 



tion, let us see what indications are afforded by the 

 reptiles. The large and universally distributed family 

 of Colubrine snakes is represented in Madagascar, not by 

 African or Asiatic genera, but by two American genera 

 — Philodryas and Heterodon, and by Herpetodryas, a 

 genus found in America and China. The other genera 

 are all peculiar, and belong mostly to widespread tropical 

 families; but two families— Lycodontidse and Viperidse, 

 both abundant in Africa and the Eastern tropics — are 

 absent. Lizards are mostly represented by peculiar genera 

 of African or tropical families, but several African genera 

 are represented by peculiar species, and there are also 

 some species belonging to two American genera of the 

 Iguanidae, a family which is exclusively American ; while 

 a genus of geckoes, inhabiting America and Australia, also 

 occurs in Madagascar. 



Relation of Madagascar to Africa. — These facts taken 

 all together are certainly very extraordinary, since they 

 show in a considerable number of cases as much affinity 

 with America as with Africa ; while the most striking 

 and characteristic groups of animals now inhabiting Africa 

 are entirely wanting in Madagascar. Let us first deal 

 with this fact, of the absence of so many of the most 

 dominant African groups. The explanation of this 

 deficiency is by no means difficult, for the rich deposits 

 of fossil mammals of Miocene or Pliocene age in France, 

 Germany, Greece, and North-west India, have demon- 

 strated the fact that all the great African mammals then 

 inhabited Europe and temperate Asia. We also know 

 that a little earlier (in Eocene times) tropical Africa was 

 cut off from Europe and Asia by a sea stretching from the 

 Atlantic to the Bay of Bengal, at which time Africa must 

 have formed a detached island -continent such as Aus- 

 tralia is now, and probably, like it, very poor in the higher 

 forms of life. Coupling these two facts, the inference 

 seems clear, that all the higher types of mammalia were 

 developed in the great Euro-Asiatic continent (which 

 then included Northern Africa), and that they only 

 migrated into tropical Africa when the two continents 

 became united by the upheaval of the sea-bottom, probably 



