348 ORIGIN OF LIFE IN AMERICA 



Ecuador (compare Fig. 14). As this western belt of land 

 was in direct communication with the West Indies by way 

 of Central America, it follows that the West Indies and 

 Ecuador were able to enter into a faunistic exchange. Many 

 instances might be quoted showing this relationship between 

 the West Indies, Central America and western South 

 America, or between parts of these areas. The head- 

 quarters of the snake-like limbless amphibians, known as 

 Coecilia, are in Ecuador. From there they have spread 

 eastward through Guiana to Brazil, and northward through 

 Colombia as far as Panama. No species is actually known 

 to occur in Central America beyond Panama. I alluded 

 to the family Anguidae on several occasions, those generally 

 limbless lizards to which the so-called glass-snake belongs. 

 One genus with well-developed limbs (Diploglossus), inhabits 

 chiefly the principal islands of the West Indies, viz., Cuba, 

 Haiti and Jamaica. In Central America it occurs in Guate- 

 mala and Costa Rica, while in South America it inhabits only 

 Ecuador and Brazil, having apparently spread into the latter 

 state from the west. 



Attention has been drawn to the fact that while the fauna 

 and flora of the Galapagos islands are principally Central 

 American and West Indian in character, they also are related 

 to those of western South America. A mere fragment only 

 of the animals and plants that passed across the lands of 

 which these islands formed part could have been preserved 

 there. Thus the Streptaxidae, a family of carnivorous snails 

 almost restricted in America to the southern continent, do 

 not occur in the Galapagos islands, although a few species 

 have penetrated to Guatemala, and one even to Haiti. The 

 genus Martinella is peculiar to Ecuador, whereas two other 

 genera, viz., Guestieria and Systrophia appear to have spread 

 from an Ecuadorian centre of dispersal to Peru, Colombia 

 and Bolivia. 



A most interesting and important case of discontinuous dis- 

 tribution is that of Clausilia, a genus of snails which I men- 

 tioned when dealing with the origin of the West Indian fauna 

 (p. 272). I then stated the reasons for my belief that 

 Clausilia had travelled across the mid-Atlantic land bridge 

 from southern Europe to the West Indies rather than by a 



