genus of cystoids, an extinct group related to the sea lily and starfish, found as fossils in Ordovician marine rocks (between 505 and 438 million years old). It is a useful guide, or index, fossil for Ordovician rocks and time.
ECHINOSPHAERITES
Meaning of ECHINOSPHAERITES in English
Britannica English vocabulary. Английский словарь Британика. 2012