I love these questions and I've pondered on this before. My suspicion is
that the ocean populations are, for the most part, isolated from bay
populations. And, not surprisingly, each has adapted shells to best suit
their environment. But there may be times when variables which dictate
isolation breakdown, allowing for an infrequent intermixing of
populations. The frilly forms may have a low survival on the open coast
but the smooth forms may fare much better within calmer bays.

Cheers,
Bob

-----Original Message-----
From: Conchologists of America List [mailto:[log in to unmask]] On
Behalf Of Roland Anderson
Sent: Wednesday, March 31, 2004 5:52 AM
To: [log in to unmask]
Subject: Nucella lamellosa "frilliness"


Hi All,
Here in the Northeastern Pacific we have a marine gastropod, Nucella
lamellosa, that has varying amounts of frills on its shells. It has been
proposed that the outer coast versions are smooth, to prevent the waves
from catching them, and those that live in protected bays like Puget
Sound have the most frills (am I using the right term for the frills?).
The problem is that in Puget Sound you can find both frilly and smooth
forms, often on the same beach, but only smooth forms on the coast, with
wave action. My qustion is then, why are smooth forms also found in
protected waters?
Roland

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