April 1, 2010
The top image shows mostly mussels, the middle image are barnacles and the third image is a chiton.
A mussel is a kind of bivalve mollusk similar to a clam (that a lot of people like steamed with a bit of garlic and oil atop a heap of linguine).
Barnacles are a completely different kind of animal, more closely related to crabs and lobster than to clams and mussels. They are not all that tasty and rarely end up in a plate of spaghetti.
Both mussels and barnacles (and chitons as well) attach themselves to rocky surfaces in the tidal zone where they are covered by the sea at high tide and exposed to the air at low tide. They also attach themselves to boats left in the water and to piers and docks. 
Chitons are mollusks with eight overlapping shells (count them), more closely related to mussels and clams than to barnacles.
Posted by: Seymour Simon
