These ones are more commonly known as the "slipper limpet", and here's how they reproduce, according to Wikipedia:

The species is a sequential hermaphrodite. The slipper limpet normally lives in stacks of up to 12 individuals, with the largest at the bottom and with increasingly smaller individuals stacked on top of one another. The largest and oldest animals, at the base of a pile are female, the younger and smaller animals at the top are male. If the females in the stack die, the largest of the males will become a female.

They have a fucking SEX PILE and if one of the females dies, one of the males just changes her sex and fills in where the last female left off. How cool is that???