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. The 
so-called waifs from the West Indies are of greater signific¬ 
ance. Dr. Pilsbry identifies Suocinea 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 con- 
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 of the.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. 
