The Opisthobranchia included species in the order Cephalaspidea ( bubble shells and headshield slugs ), the sacoglossans, anaspidean sea hares, pelagic sea angels, sea butterflies, and many families of the Nudibranchia.
22.
""'Peracle charlotteae " "'is an extinct species of fossil pelagic sea snail, or " sea butterfly ", a planktonic marine gastropod mollusk in the family Peraclidae.
23.
""'Limacina rangii " "'is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies ( Thecosomata ).
24.
Adults feed in a predator-prey relationship almost exclusively on the sea butterflies of the genus " Limacina " : on " Limacina helicina " and on " Limacina retroversa ".
25.
""'Gleba cordata " "'is a species of sea butterfly, a floating and swimming sea snail or sea slug, a pelagic marine gastropod mollusk in the family Cymbuliidae.
26.
""'Cavolinia tridentata " "'is a species of sea butterfly, a floating and swimming sea snail or sea slug, a pelagic marine gastropod mollusk in the family Cavoliniidae.
27.
""'Limacina retroversa " "'is a species of swimming predatory sea snail in the family Limacinidae, that belong to the group commonly known as sea butterflies ( Thecosomata ).
28.
""'Limacina helicina " "'is a species of small swimming predatory sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies ( Thecosomata ).
29.
:The clades Thecosomata and "'Gymnosomata "'are small pelagic gastropods known as " sea butterflies " and " sea angels "; these are usually simply known as " pteropods " but can also loosely be called sea slugs, especially the Gymnosomata, which have no shell as adults.
