JUST WHEN YOU THINK YOU KNOW SOMETHING......

After all these years on the beach I was under the false impression that I actually knew something....I doubt it.  We have come across two mysteries that as yet nobody we've asked has been able to solve.
First are these clam shells with interesting grooves in them......sort of look like ditches made by a run amok "Bertha" but more likely another mollusk using the radula.  So far my best guess is a drunken Moon Snail.  We have top people working on this mystery.
The second mystery is solved.  The mollusk in the bottom image is a Slipper Shell.  Still not certain the species as there are a couple of similar ones around, but Crepipatella dorsata is the call.

Grooved Butter Clam shell (drill hole at top is from Moon Snail

Clam shell with multiple grooves

Slipper Shell (Crepipatella dorsata)