Update: I realized I misspoke about the type of creature... it's a
mussel, not an oyster.
I couldn't find any concrete info online, so I contacted the Virginia
Institute of Marine Science today. Apparently, it is not common, and
it doesn't seem to have been reported from this area before. One of
the researchers is going to look at more pictures that I sent
tonight, check around, and get back to me.
I'm sorry if anyone tried to check out the picture the other night
when our server was down. A fiber-optic cable was cut and we lost
service for almost 24 hours, but everything's back to normal now.
Carol J. Bova
The Eclectic Lapidary