I found mollusc shells on the beach yesterday.
Oh nice, which beach did you find the shells on?
Just on a beach in San Diego.
That's neat. Are there usually a lot of mollusc shells there?
Mollusc shell
The mollusc (or mollusk) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
The ancestral mollusc is thought to have had a shell, but this has subsequently been lost or reduced on some families, such as the squid, octopus, and some smaller groups such
with a series of concentric growth rings parallel with the margin. In the living animal, the valves are covered by the periostracum, a thin grey protective layer of protein which is part of the shell. This layer has usually been stripped away by sand and surf by the time that the empty shells are washed up on the beach, and the valves are usually found singly, because the muscles that hold them together are weak. Internally, the live mollusc has a powerful muscular foot and a pair of long, fused siphons