I doubt temperature is the explanation. Several of things that you didn't
find (Simnias, seawhips, olivellas) are near the northern end of their
range in South Carolina. Unfortunately, in most cases we don't have enough
information to judge if or why the fauna has changed in a particular area.

This emphases the need for long term observation and collecting of common
species in supposedly well-known areas. It's the only way to prove that
things have changed and to start the search for explanations of change. As
an example, a few days ago I had a request for specimens of oysters
collected alive in Chesapeake Bay and its tributaries on a known date
before 1945. They are needed to standardize carbon 14 values before the
signal was contaminated by atom bomb detonations. This will allow accurate
age determination of oysters in cores drilled in Chesapeake Bay, which
might help in understanding environmental changes in the bay. (We had only
five such lots.)

By the way, I had a similar request for Pitar and Laevicardium from
Caribbean Panama, collected live pre-1945, but we had none. If any of you
have any, please contact me.

Gary

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Gary Rosenberg, Ph.D.                     [log in to unmask]
Malacology & Invertebrate Paleontology    gopher://erato.acnatsci.org
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