Tylodina perversa

Tylodina perversa, common names the 'yellow tylodina' or 'yellow umbrella slug', is a species of sea snail or false limpet, a marine opisthobranch gastropod mollusk in the family Tylodinidae. This opisthobranch has a limpet-like shell which is composed primarily of protein, not calcium carbonate. This species of false limpet occurs in the northeastern Atlantic including the British Isles and the Mediterranean Sea. T. perversa feeds on the sponge species Aplysina aerophoba.