Answer: obelia

AnswerCrossword Clue
OBELIAMosslike growth on marine rock
obeliaa marine hydroid also pl of OBELION
obeliaany of a genus (Obelia) of small colonial marine hydroids with colonies branched like trees
obeliacolonial hydroid of the genus Obelia, common in temperate seas and appearing as a delicate, mosslike growth on rocks, pilings, etc.