( n. pl. )
An order of irregular sea urchins, usually having a more or less heart-shaped shell with four or five petal-like ambulacra above. The mouth is edentulous and situated anteriorly, on the under side.
( n. pl. )
An order of irregular sea urchins, usually having a more or less heart-shaped shell with four or five petal-like ambulacra above. The mouth is edentulous and situated anteriorly, on the under side.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012