Barnea dilatata; a species of piddock
A type of boring clam found in marine environments. The name is usually written in katakana as ウミタケ.
The umitake is a bivalve that lives by boring holes into rocks.
Kanji form is rare; the word is usually written in kana.
Compound of 海 (umi, 'sea') + 茸 (take, 'mushroom'), likely from the shape of the siphon resembling a mushroom. The exact derivation is uncertain.