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)|