> It may not be so bleak as you may think. Henry van der Schalie (loc. cit.)
> reported finding 13 instances of reversal of lateral teeth among nine
> species if North American naiades. These were not included in an earlier
> report by Isaac Lea of six instances involving five species (Lea, 1860).
>
> I think there are plenty more reversed specimens awaiting discovery in
> museum suites, where diagnosis is much more efficient than in  the field.
>
> Harry

The tally for unionids will also be affected by how you count
"Alasmidonta" heterodon, a species characterized by partial reversal
of the dentition relative to most species.

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

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