Dear Harry,

Firstly: thanks for your info. However it seems that the genus Cepaea is
an old-world genus according to L.M. Cook, A two-stage model for Cepaea
polymorphism. (http://www.jstor.org/pss/56929).

Therefore I'd think that migration of Cepaea species would in a
east-west direction across the Atlantic.
When looking at a map the sea depth (pleistocene-holocene period) even
at the most shallow locations would preclude a land-bridge transfer of
Cepaea species.
Which leaves in my opinion four options open:

1) Travel via sea-currents (unlikely in my opinion since sea-currents in
the North Atlantic generally run west-east)
2) Transport by animal (birds)
3) Transport by human travel.
4) A combination of the three modi above.

Cepaea hortensis is known from a few isolated spots on the south coast
of Iceland. In all the discussions about norsemen, etc. one group of
people who could have served as transport vector seem to be missing:
that is the Inuit (or wrongly named: Eskimo). These people traveled the
Arctic regions of the world long before Norsemen.
My personal bets are on the Inuit therefore, possibly in combination
with the other modi of transport who got the genus Cepaea from the old
world into the new.

Sincerely, Erick

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