"Have a look at that dark purple blob on the left, there." With those words, scientists aboard the Exploration Vessel Nautilus uncovered a marine mystery: a small purple orb tucked halfway under a rock off the coast of California. Researchers are so far stumped as to what the colorful, bumpy little ball might be. Their best guess is that it might be a gastropod (a mollusk such as a snail or slug that belongs to the class Gastropoda) called a pleurobranch — and possibly a new species.