M-750 GIANT HEART COCKLE, Dinocardium robustum
It has heavy ribbed, heart-shaped shell, mottled brown and purple. When removed from the water, it will violently catapult itself about with its pointed foot, a ridiculous sight resembling a great tongue thrust out of a wide grinning mouth. Size 8-12 cm.
VIDEOS
ADDITIONAL READING
https://www.mitchellspublications.com/guides/shells/articles/0007/