From the Merriam-Webster dictionary:
Ham·i·noea noun \ˌhaməˈnēə\
Definition of HAMINOEA
: a common genus of bubble shells (family Akeridae) of the Pacific coast of No. America with a shell so thin that the pulsation of the heart of the translucent yellowish brown animal within is commonly visible through it.
I've got three new bubble shells in the aquarium, and they're big enough (over an inch long) for me to see this. And they hang out near the water surface, so I've got video, too!