California mussel
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The California mussel is a large edible mussel, a marine bivalve mollusk in the family Mytilidae.
Large California mussel beds, north Moonstone beach near Cambria, California. Brown, furry-looking seaweed is Gloiopeltis furcata, both in the mid to upper intertidal zones.
Periostracum
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The periostracum is a thin, organic coating that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and cla
The shell of Stenotrema florida, a land snail or terrestrial gastropod. The periostracum of this species has minute hairs, giving the snail a velvety feel
A yellowish tan periostracum is visible on the lower two thirds of this juvenile (8 cm) valve of the marine bivalve Spisula solidissima
The dark periostracum is flaking off of this dried-out valve of the "ocean quahog", marine bivalve Arctica islandica, from Wales
Fresher valves of Arctica islandica with periostracum intact. Note that the periostracum is partially worn off on the umbo, this is because the umbo is older than the rest of the shell and also projects more: it has been exposed to more abrasion during the life of the clam