Memorial Shell

The Memorial Shell is a treasure in Pikmin 2 that is actually the bottom half of a scallop shell. It is found in 3rd sublevel of the Citadel of Spiders, and is completely buried in the ground, so White Pikmin are needed to dig it up.

Captain Olimar's Journal
"I've observed several species of shell-dwelling creatures inhabiting the Perplexing Pool. One of these feisty beasts forms a spherical gem within the meaty depths of its shell. In a way, this gem could be considered this creature's lifework. I consider my children my life's work."

Sales Pitch
"All that remains of a monster shellfish is a sparkle, the sole proof of its existence. Does this not make you want to treasure it?"