magoito beach, portugal

steromphala umbilicalis flat top shell gibbula species small sea snail snails summer season algae atlantic ocean teromphala marine gastropod mollusk trochidae spiral ridges spots striped european waters sublittoral rocky shore conoidal thick solid rosered lines seawalled environs interstitial areas animals fauna nature overcast macro biology invertebrate life magoito beach portugal sao joao das lampas lisbon sintra iodine rich rock pools low tide geological significance shell display roundish pebble