Jose:
I don't know of any published information, but I can relate that over 30
years ago I collected a pomum with a similar abnormality - two separate and
fully formed opercula which overlapped each other.  The specimen was
collected on Sanibel.  I briefly discussed the find with Elsie Malone (the
younger) and we thought that perhaps the mantle might have been damaged in
that area which had prompted the animal to develop a secondary operculum.
It was impossible to determine which one of them had been the older operc,
i.e., the one on top or the one underneath.
Cheers,
Ed Dunham
 
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> From: Jose H. Leal <[log in to unmask]>
> To: [log in to unmask]
> Subject: Double opercula
> Date: Thursday, March 05, 1998 8:18 AM
>
> Fellow Conch-Lers,
>
> Nicholas Zantopp, a young (yes, 11 years old) shell collector from Fort
> Lauderdale, FL, is visiting the collection area of the Shell Museum. He
and
> his mom came to participate in the (once again) excellent Sanibel Shell
> Show. I am trying to find, following his request, if any of you out there
> know of any published information on the phenomenon of double opercula.
He
> has found a medium-size apple murex (Phyllonotus pomum) that had two
> opercula (the animal and shell otherwise look normal); far I couldn't
find
> any paper(s) or other information that could help Nicholas in his quest
for
> the double-opercular truth. Best to all,
>
>
__________________________________________________________________________
> Jose H. Leal, Ph.D.
> Director-The Bailey-Matthews Shell Museum
> Editor-THE NAUTILUS
> [log in to unmask]
> 3075 Sanibel-Captiva Road
> Sanibel, FL 33957 USA
> (941) 395-2233; fax (941) 395-6706