Hello folks,

I just discovered something I never knew before (at least I think I did) and
I am wondering if anyone can confirm this.  I was photographing some
opercula for a presentation I am doing next week at the local shell club
meeting.  I wanted to make the point that all opercs have a conchiolin base,
even though some of them subsequently add a calcareous layer.  So I was
looking through my shells to find some good examples of calcareous opercs
with the inner conchiolin layer still present.  Turbinidae - no problem.
Naticidae - no problem.  But after looking at a hundred or so Neritidae
opercs, I could not find a single one with the inner surface covered with
conchiolin.  However, some of them did seem to show a bit of corneous fringe
at the margins.  I then started looking at them on edge, under the
microscope, and many of them have the appearance of a sandwich - calcareous
on both sides, with a (presumably) conchiolin layer in the middle??  I
theorize then, that moon snails and turbans calcify only the outer side of
their opercs, while nerites deposit calcium on both the inner and outer
surfaces.  However, I don't remember ever seeing this in print.  Can anyone
confirm this?  Or am I misinterpreting things here?

On another subject, [log in to unmask] no longer exists.  Well, PaulCyp does,
but home.com does not.  I am now [log in to unmask]

Regards,
Paul M.