kevnkev
Dirona
In short, you do not need a permit or licence to collect many things on the beach
This was the way miscellaneous invertebrates used to be regulated, up through last year.
This year's fishing regulations pamphlet (pdf in this link) says,
Page 19 defines shellfish asAn unclassified marine invertebrate is any shellfish species not defined as shellfish on page 19. Examples include: shore crabs, graceful crabs, sea stars, sand dollars, moon snails, shore snails, marine worms and nudibranchs. NO HARVEST ALLOWED" (Dept. of Fish and Wildlife's emphasis).
Shellfish Includes Dungeness, red rock, tanner, king, and box crab; razor clams, and all other marine clams existing in a wild state; oysters, geoducks, shrimp, California sea cucumbers, sea urchins, scallops, goose barnacles, cockles, mussels, squid, octopus, and crawfish.
I think the previous thought on unclassified shellfish was that not enough people would be interested in collecting them, so no concerns about overharvesting. Current regulations sound more precautionary - unless someone at the state is explicitly monitoring the stocks of a species they don't want the species to run the risk of overexploitation.
Sounds like if you're willing to limit your local tank to the species called out on the list of shellfish all you need is a state-issued recreational shellfishing permit, but if you want more varied diversity you're out of luck.
Disclaimer - these are regulations for recreational collecting. Different permits exist for research and educational purposes.