> My question is; In your estimation, has there been any shell family,
> common under 50 years ago but now..or very recently becoming a prized
> rarity.

In the past 50 years, many unionoids have gone extinct or become
extremely rare, though some human-caused extinctions date back earlier
than that.  Similar events have happened in the pleurocerids and other
freshwater groups.  Some of the species had been very abundant in
historical collections.  Similar declines can be seen in some
terrestrial groups.

--
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"

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