Veliger

9 day old veliger of the nudibranch Tritonia diomedea with various organs and structures labeled. Larval size about 200 um on its long axis.
Veliger of sea hare Dolabrifera dolabrifera, with two rows of cilia visible

A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells.