The aplustrum amplustre is a species of sea snail also known as the royal paper bubble, the swollen bubble and the ship’s flag snail. Their shells are too small for their bodies so life is presumably a struggle of not quite fitting in. They tend to live in warm, tropical oceans from the Indian through to the Pacific. They are nocturnal and tend to bury themselves in the sand for camouflage so they are rare to see – the second link below has some lovely photos. I don’t know how these little dudes got the attention of the Singapore postal service in 1977, but I’m quite glad they did (seriously, check out the second link…).