These are common on all limestone rocks in the area. Night low tide on the city dock (-5 ft), on limstone riprap.
At the end of Dock H at the Woodley island marina, Humboldt Bay, with Mytilus, sponges, tunicates, eelgrass, etc.
I have a shell that broke, that is exactly like this one except a red-pinking color. Shape is interesting for a bivalve.
Single shell found lodged under Hormosira
@invertzoo I thought you might know what this is. about 30 million years old. I also put 4 more observations of different fossil shells all under bivalves. Just hoping you would know what they are.
Small specimen of a little known brachiopod found mainly in S. CA but also described as far north as Tomales Bay. It has turned up in a few recent surveys in Elkhorn Slough. ID and info from John Pearse and Mark Silberstein.
Brachiopods, phylum Brachiopoda, are marine animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major groups are recognized, articulate and inarticulate. Articulate brachiopods have toothed hinges and simple opening and closing muscles, while inarticulate brachiopods have untoothed hinges and a more complex system...