I was wading in the local creek (central Indiana) when I noted a single valve in
the foot-deep water. Hoping to stir up its mate, I came up, instead, with a
live clam. At a mere 3/4-inch across, it was rather small,... to someone who
has seen three foot wide Tridachna gigas in situ.

Since it is illegal in this state to disturb or molest ANY mollusk, I tossed it
back after noting that the valves were dark brown at the hinge but quickly gave
way to an algae-green color other the rest of the shell. I estimated about 15
"growth rings" on it.

The questions are two: 1.) Does anyone care to guess what variety of plecypod
this is?, and 2.) What time interval is associated with the growth marks,...
annual, lunar, sesquiquadrate aspects to the synodic period of Venus,.. or
what?!

Bob Dayle

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