opelet
/ˈəʊplɪt/noun
More fully opelet anemone. Any of several sea anemones of the genus Anemonia, characterized by long tentacles that cannot be fully retracted; especially A. sulcata, which occurs in both brown and green forms and is found in the north-east Atlantic and the Mediterranean.
Origin
Mid 19th century; earliest use found in Philip Gosse (1810–1888), zoologist and religious writer. From ope + -let, with allusion to the fact that the anemone's tentacles cannot be retracted.