192 ORIGIN OF LIFE IN AMERICA 



although some .members of it are probably indigenous. The 

 remainder include several snails, only once recorded, and 

 not again found on the island in recent times. iThe 

 so-called waifs from the West Indies are of greater signific- 

 ance. Dr. Pilsbry identifies Succinea bermudensis with 

 S. barbadensis, yet acknowledges that the shells of this 

 genus are peculiarly uncharacteristic, and that species of 

 different regions frequently resemble each other. All oon- 

 chologists, however, are agreed that the semi-amphibious 

 amber-snail (Succinea), with its almost world- wide distribu- 

 tion, must be a very ancient one. The mere fact of several 

 Bermudan species being identical with West Indian ones 

 is no proof that they were conveyed to Bermuda by accidental 

 means of transport. I have argued this point again and again, 

 but it is a widespread assumption which can only be effectu- 

 ally disproved by palaeontological evidence. No such evidence 

 is available in the majority of cases. Yet of some of these sup- 

 posed accidentally and recently introduced species of Bermuda 

 I might mention Rumina decollata. It is certainly native in 

 the Mediterranean region, where it exists, as a relict othe.past, 

 and I have given a map of its range in my work on European 

 animals.* The family Stenogyridae, to which it belongs, is 

 an entirely tropical one. Rumina decollata has adapted itself 

 to the European climate, though its shape has remained un- 

 changed since Oligocene times. It has been known to exist 

 outside Europe in Cuba, South Carolina and Bermuda. Are 

 we justified in the assumption that this exceedingly old 

 member of a tropical family of snails has been accidentally 

 introduced into these localities ? I think not, and yet this 

 surmise is received by almost everybody as an established 

 fact. 



The really interesting members of the Bermudan fauna of 

 mollusks are those styled "autochthonous" by Dr. Pilsbry, 

 viz., Helicina convexa, Thysanophora hypolepta, all the 

 species of Poecilozonites, and the slug Veronicella schivelyae. 



I have already dwelt upon the distribution of the genus 

 Helicina (p. 158), and on its occurrence in the Oligocene 

 Silex beds of Tampa in Florida, and have indicated that it 



* Scharff, E. F., "European Animals," p. 222. 



