MORE GROOVED CLAM SHELLS

An absolutely perfect day for the beach......and some more grooved clam shells to add to the mystery.
The ones below were found at Schmitz Park beach in West Seattle.  One had limpets on the outside of the shell and narrow grooves on the inside.  A few others had worm tubes attached to the shells that left marks where removed but not real grooves.  So we are no nearer to the answer to the mystery except that our octopus expert does not see this as the work of an octopus...so I'm dropping that suspect.  
Just to keep things interesting a jellyfish showed up with what appears to be 10 lobes....red in color and only palm size.  Will need some work on the keys to figure this species out as our common Fried-egg Jellyfish has 16 lobes and the Red Sea Blubber has 8.  

Opalescent Sea Slugs are showing up on Moon Snail sand collars along with their eggs.....as well as the green eggs of the green polychaete worm Phyllodoce williamsi.

Worm tube from inside clam shell with some shell material on tube

Grooves on inside of clam shell #1

Limpets on outside of clam shell #1

Worm tube on outside of clam shell

Same clam shell as above with worm tube removed

Grooved clam shell with perhaps partial Moon Snail drill hole at top

Grooved clam shell with out of place Moon Snail partial drill hole (groove at upper right)

Green worm eggs on sand collar (Phyllodoce williamsi)

Jellyfish species unidentified with what appears to be 10 lobes

Same jellyfish as above swimming

Opalescent Sea Slugs on sand collar

Purple Sea Star with wasting disease...possibly healing?