Common Keyhole Limpet
Shell is shaped like an oval cone with many ribs radiating a small keyholelike opening at the apex near the center of the shell. The limpet ejects waste and water that has passed over the gills through the opening.
The limpet feeds by scraping algae from rocks and it is a common snail in tidal pools. Its powerful foot creates strong suction to keep waves from washing it off the rocks and to hold it secure until the next high tide.
Limpets generally stay in one area their entire life, never venturing very far and will return to their exact spot on a rock after they finish feeding. Generally nocturnal, keyhole limpets rarely feed unless submerged in water.
Atlantic Plate Limpet
Also known as the tortoise shell limpet, it is found intertidally on rocks and in tidal pools from Massachusetts north to the Arctic.