Limacina is a genus of swimming predatory sea snails commonly known as sea butterflies in the family Limacinidae. This genus contains some of the world's most abundant gastropod species.

Etymological meaning of the generic name Limacina is "snail-like".

As pelagic marine gastropods, Limacina swim by flapping their parapodia, inspiring the common name sea butterflies.

Sea butterflies are part of the clade Thecosomata. Sea angels, similar to Limacina, are in the order Gymnosomata. Both of these orders are still referred to as "pteropods". Sea butterflies of the order Thecosomata have a shell, while sea angels in the order Gymnosomata do not.

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