What is this A shell that's known for its mother-of-pearl (It lives in the ocean)?

Where does the River Great Ouse start? What is the capital city known as the city of love? Which two rivers join at Sutter's point? In which direction would you travel to get from mount Everest to thenile river? Where is the Vin on a gulf stream Motor home? What do you climb up the steps to see the Eiffel Tower? How tall is Tom Burlinson Man from Snowy River? What were the Parthenon columns made of? Does lake Okeechobee have creeks? Disneyland Tickets? What is a part of sea of ocean that cuts into a mass of land? What does sur la mean? Why did they move west from Illinois in the 1840s and why to the Great Salt Lake Valley? how high is should a parapet wall be? Does the great wall of china enter any other countries but china? What is the opposite of Dame? What does the pacific rim include? Why is the sea side called the seaside? In what was the frontier it the US pushed west of the Mississippi River? Are there jellyfish in the potomac river?