Crossword clue: the free-swimming larva of sea urchins and ophiurans, having several long stiff processes inclosing calcareous rods.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
a large genus of fungi belonging to the family Pluteaceae; the shape of the cap resembles a roof; often abundant early i