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.