Nautilus

The nautilus is an aquatic mollusk native to Earth.

When Spock tried to match the sound of the Whale Probe to the sound of an Earth animal aboard the Klingon Bird-of-Prey HMS Bounty, a nautilus was one of the animals shown. 

For some time, Captain Jean-Luc Picard kept a nautilus shell in his ready room aboard the USS Enterprise (NCC-1701-D).